

A000522


Total number of ordered ktuples (k=0..n) of distinct elements from an nelement set: a(n) = Sum_{k=0..n} n!/k!.
(Formerly M1497 N0589)


269



1, 2, 5, 16, 65, 326, 1957, 13700, 109601, 986410, 9864101, 108505112, 1302061345, 16926797486, 236975164805, 3554627472076, 56874039553217, 966858672404690, 17403456103284421, 330665665962404000, 6613313319248080001, 138879579704209680022, 3055350753492612960485, 70273067330330098091156
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OFFSET

0,2


COMMENTS

Total number of permutations of all subsets of an nset.
Also the number of onetoone sequences that can be formed from n distinct objects.
Old name "Total number of permutations of a set with n elements", or the same with the word "arrangements", both sound too much like A000142.
Related to number of operations of addition and multiplication to evaluate a determinant of order n by cofactor expansion  see A026243.
a(n) is also the number of paths (without loops) in the complete graph on n+2 vertices starting at one vertex v1 and ending at another v2. Example: when n=2 there are 5 paths in the complete graph with 4 vertices starting at the vertex 1 and ending at the vertex 2: (12),(132),(142),(1342),(1432) so a(2) = 5.  Avi Peretz (njk(AT)netvision.net.il), Feb 23 2001; comment corrected by Jonathan Coxhead, Mar 21 2003
Also row sums of Table A008279, which can be generated by taking the derivatives of x^k. For example, for y = 1*x^3, y' = 3x^2, y" = 6x, y'''= 6 so a(4) = 1 + 3 + 6 + 6 = 16.  Alford Arnold, Dec 15 1999
a(n) is the permanent of the n X n matrix with 2s on the diagonal and 1s elsewhere.  Yuval Dekel, Nov 01 2003
Stirling transform of A006252(n1) = [1,1,1,2,4,14,38,...] is a(n1) = [1,2,5,16,65,...].  Michael Somos, Mar 04 2004
Number of {12,12*,21*} and {12,12*,2*1}avoiding signed permutations in the hyperoctahedral group.
a(n) = b such that Integral_{x=0..1} x^n*exp(x) dx = ab*exp(1).  Sébastien Dumortier, Mar 05 2005
a(n) is the number of permutations on [n+1] whose lefttoright record lows all occur at the start. Example: a(2) counts all permutations on [3] except 231 (the last entry is a record low but its predecessor is not).  David Callan, Jul 20 2005
a(n) is the number of permutations on [n+1] that avoid the (scattered) pattern 123. The vertical bar means the "3" must occur at the end of the permutation. For example, 21354 is not counted by a(4): 234 is an offending subpermutation.  David Callan, Nov 02 2005
Number of deco polyominoes of height n+1 having no reentrant corners along the lower contour (i.e., no vertical step that is followed by a horizontal step). In other words, a(n)=A121579(n+1,0). A deco polyomino is a directed columnconvex polyomino in which the height, measured along the diagonal, is attained only in the last column. Example: a(1)=2 because the only deco polyominoes of height 2 are the vertical and horizontal dominoes, having no reentrant corners along their lower contours.  Emeric Deutsch, Aug 16 2006
Unreduced numerators of partial sums of the Taylor series for e.  Jonathan Sondow, Aug 18 2006
a(n) is the number of permutations on [n+1] (written in oneline notation) for which the subsequence beginning at 1 is increasing. Example: a(2)=5 counts 123, 213, 231, 312, 321.  David Callan, Oct 06 2006
a(n) is the number of permutations (written in oneline notation) on the set [n + k], k >= 1, for which the subsequence beginning at 1,2,...,k is increasing. Example: n = 2, k = 2. a(2) = 5 counts 1234, 3124, 3412, 4123, 4312.  Peter Bala, Jul 29 2014
a(n) and (1,2,3,4,5,6,7,...) form a reciprocal pair under the list partition transform and associated operations described in A133314.  Tom Copeland, Nov 01 2007
Consider the subsets of the set {1,2,3,...,n} formed by the first n integers. E.g., for n = 3 we have {}, {1}, {2}, {3}, {1,2}, {1,3}, {2,3}, {1,2,3}. Let the variable sbst denote a subset. For each subset sbst we determine its number of parts, that is nprts(sbst). The sum over all possible subsets is written as Sum_{sbst=subsets}. Then a(n) = Sum_{sbst=subsets} nprts(sbst)!. E.g., for n = 3 we have 1!+1!+1!+1!+2!+2!+2!+3!=16.  Thomas Wieder, Jun 17 2006
For positive n, equals 1/BarnesG(n+1) times the determinant of the n X n matrix whose (i,j)coefficient is the (i+j)th Bell number.  John M. Campbell, Oct 03 2011
a(n) is the number of n X n binary matrices with i) at most one 1 in each row and column and ii) the subset of rows that contain a 1 must also be the columns that contain a 1. Cf. A002720 where restriction ii is removed.  Geoffrey Critzer, Dec 20 2011
Number of restricted growth strings (RGS) [d(1),d(2),...,d(n)] such that d(k) <= k and d(k) <= 1 + (number of nonzero digits in prefix). The positions of nonzero digits determine the subset, and their values (decreased by 1) are the (left) inversion table (a rising factorial number) for the permutation, see example.  Joerg Arndt, Dec 09 2012
Number of a restricted growth strings (RGS) [d(0), d(1), d(2), ..., d(n)] where d(k) >= 0 and d(k) <= 1 + chg([d(0), d(1), d(2), ..., d(k1)]) and chg(.) gives the number of changes of its argument. Replacing the function chg(.) by a function asc(.) that counts the ascents in the prefix gives A022493 (ascent sequences).  Joerg Arndt, May 10 2013
The sequence t(n) = number of i <= n such that floor( e i! ) is a square is mentioned in the abstract of Luca & Shparlinski. The values are t(n)=0 for 0 <= n <= 2 and t(n) = 1 for at least 3 <= n <= 300.  R. J. Mathar, Jan 16 2014
a(n) is the number of ways at most n people can queue up at a (slow) ticket counter when one or more of the people may choose not to queue up. Note that there are C(n,k) sets of k people who quene up and k! ways to queue up. Since k can run from 0 to n, a(n) = Sum_{k=0..n} n!/(nk)! = Sum_{k=0..n} n!/k!. For example, if n=3 and the people are A(dam), B(eth), and C(arl), a(3)=16 since there are 16 possible lineups: ABC, ACB, BAC, BCA, CAB, CBA, AB, BA, AC, CA, BC, CB, A, B, C, and empty queue.  Dennis P. Walsh, Oct 02 2015
As the row sums of A008279, Motzkin uses the abbreviated notation $n_<^\Sigma$ for a(n).
The piecewise polynomial function f defined by f(x) = a(n)*x^n/n! on each interval [ 11/a(n), 11/a(n+1) ) is continuous on [0,1) and lim_{x>1} f(x) = e.  Luc Rousseau, Oct 15 2019
a(n) is composite for 3 <= n <= 2015, but a(2016) is prime (or at least a strong pseudoprime): see Johansson link.  Robert Israel, Jul 27 2020
In general, sequences of the form a(0)=a, a(n) = n*a(n1) + k, n>0, will have a closed form of n!*a + floor(n!*(e1))*k.  Gary Detlefs, Oct 26 2020
a(2*n) is odd and a(2*n+1) is even. More generally, a(n+k) == a(n) (mod k) for all n and k. It follows that for each positive integer k, the sequence obtained by reducing a(n) modulo k is periodic, with the exact period dividing k. Various divisibility properties of the sequence follow from this; for example, a(5*n+2) == a(5*n+4) == 0 (mod 5), a(25*n+7) == a(25*n+19) == 0 (mod 25) and a(13*n+4) == a(13*n+10)== a(13*n+12) == 0 (mod 13). (End)


REFERENCES

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 75, Problem 9.
J.M. De Koninck, Ces nombres qui nous fascinent, Entry 65, p. 23, Ellipses, Paris 2008.
J. M. Gandhi, On logarithmic numbers, Math. Student, 31 (1963), 7383.
J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 16.
D. Singh, The numbers L(m,n) and their relations with prepared Bernoulli and Eulerian numbers, Math. Student, 20 (1952), 6670.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

F. Ardila, F. Rincón, and L. Williams, Positroids, noncrossing partitions, and positively oriented matroids, in FPSAC 2014, Chicago, USA; Discrete Mathematics and Theoretical Computer Science (DMTCS) Proceedings, 2014, 555666.
Olivier Bodini, Antoine Genitrini, and Mehdi Naima, Ranked Schröder Trees, arXiv:1808.08376 [cs.DS], 2018.
Xing Gao and William F. Keigher, Interlacing of Hurwitz series, Communications in Algebra, 45:5 (2017), 21632185, DOI: 10.1080/00927872.2016.1226885. See Ex. 2.16.
Lorenz Halbeisen and Norbert Hungerbuehler, Number theoretic aspects of a combinatorial function, Notes on Number Theory and Discrete Mathematics 5 (1999) 138150. (ps, pdf)
J. Sondow and K. Schalm, Which partial sums of the Taylor series for e are convergents to e? (and a link to the primes 2, 5, 13, 37, 463), II, arXiv:0709.0671 [math.NT], 20062009; Gems in Experimental Mathematics (T. Amdeberhan, L. A. Medina, and V. H. Moll, eds.), Contemporary Mathematics, vol. 517, Amer. Math. Soc., Providence, RI, 2010.


FORMULA

a(n) = n*a(n1) + 1, a(0) = 1.
a(n) = n! * Sum_{k=0..n} 1/k! = n! * (e  Sum_{k>=n+1} 1/k!).  Michael Somos, Mar 26 1999
a(0) = 1; for n > 0, a(n) = floor(e*n!).
E.g.f.: exp(x)/(1x).
Integral representation as nth moment of a nonnegative function on a positive halfaxis: a(n) = e*Integral_{x=0..infinity} (x^n*e^(x)*Heaviside(x1).  Karol A. Penson, Oct 01 2001
Formula, in Mathematica notation: Special values of Laguerre polynomials, a(n)=(1)^n*n!*LaguerreL[n, 1n, 1], n=1, 2, ... . This relation cannot be checked by Maple, as it appears that Maple does not incorporate Laguerre polynomials with second index equal to negative integers. It does check with Mathematica.  Karol A. Penson and Pawel Blasiak ( blasiak(AT)lptl.jussieu.fr), Feb 13 2004
G.f.: Sum_{k>=0} k!*x^k/(1x)^(k+1). a(n) = Sum_{k=0..n} (1)^(nk)*binomial(n, k)*k^(nk)*(k+1)^k.  Vladeta Jovovic, Aug 18 2002
a(n) = e*Gamma(n+1,1) where Gamma(z,t) = Integral_{x>=t} e^(x)*x^(z1) dx is incomplete gamma function.  Michael Somos, Jul 01 2004
a(n) = 1 + n + n*(n1) + n*(n1)*(n2) + ... + n!.  Jonathan Sondow, Aug 18 2006
a(n) = Sum_{k=0..n} binomial(n,k) * k!; interpretation: for all ksubsets (sum), choose a subset (binomial(n,k)), and permutation of subset (k!).  Joerg Arndt, Dec 09 2012
a(n) = Sum_{k=0..n} A094816(n, k), n>=0 (row sums of PoissonCharlier coefficient matrix).  N. J. A. Sloane, Nov 10 2007
Act on 1/(1x) with 1/(1xDx) = Sum_{j>=0} (xDx)^j = Sum_{j>=0} x^j*D^j*x^j = Sum_{j>=0} j!*x^j*L(j,:xD:,0) where Lag(n,x,0) are the Laguerre polynomials of order 0, D the derivative w.r.t. x and (:xD:)^j = x^j*D^j. Truncating the operator series at the j = n term gives an o.g.f. for a(0) through a(n) consistent with Jovovic's.
These results and those of Penson and Blasiak, Arnold, Bottomley and Deleham are related by the operator A094587 (the reverse of A008279), which is the umbral equivalent of n!*Lag[n,(.)!*Lag[.,x,1],0] = (1D)^(1) x^n = (1)^n * n! Lag(n,x,1n) = Sum_{j=0..n} binomial(n,j)*j!*x^(nj) = Sum_{j=0..n} (n!/j!)*x^j. Umbral substitution of b(.) for x and then letting b(n)=1 for all n connects the results. See A132013 (the inverse of A094587) for a connection between these operations and 1/(1xDx).
(End)
a(n) = n!*e  1/(n + 1/(n+1 + 2/(n+2 + 3/(n+3 + ...)))).
Asymptotic result (Ramanujan): n!*e  a(n) ~ 1/n  1/n^3 + 1/n^4 + 2/n^5  9/n^6 + ..., where the sequence [1,0,1,1,2,9,...] = [(1)^k*A000587(k)], for k>=1.
a(n) is a difference divisibility sequence, that is, the difference a(n)  a(m) is divisible by n  m for all n and m (provided n is not equal to m). For fixed k, define the derived sequence a_k(n) = (a(n+k)a(k))/n, n = 1,2,3,... . Then a_k(n) is also a difference divisibility sequence.
For example, the derived sequence a_0(n) is just a(n1). The set of integer sequences satisfying the difference divisibility property forms a ring with termwise operations of addition and multiplication.
Recurrence relations: a(0) = 1, a(n) = (n1)*(a(n1) + a(n2)) + 2, for n >= 1. a(0) = 1, a(1) = 2, Dfinite with recurrence: a(n) = (n+1)*a(n1)  (n1)*a(n2) for n >= 2. The sequence b(n) := n! satisfies the latter recurrence with the initial conditions b(0) = 1, b(1) = 1. This leads to the finite continued fraction expansion a(n)/n! = 1/(11/(21/(32/(4...(n1)/(n+1))))), n >= 2.
Limit_{n>infinity} a(n)/n! = e = 1/(11/(21/(32/(4...n/((n+2)...))))). This is the particular case m = 0 of the general result m!/e  d_m = (1)^(m+1) *(1/(m+2 1/(m+3 2/(m+4 3/(m+5 ...))))), where d_m denotes the mth derangement number A000166(m).
For sequences satisfying the more general recurrence a(n) = (n+1+r)*a(n1)  (n1)*a(n2), which yield series acceleration formulas for e/r! that involve the PoissonCharlier polynomials c_r(n;1), refer to A001339 (r=1), A082030 (r=2), A095000 (r=3) and A095177 (r=4).
For the corresponding results for the constants log(2), zeta(2) and zeta(3) refer to A142992, A108625 and A143007 respectively.
(End)
G.f. satisfies: A(x) = 1/(1x)^2 + x^2*A'(x)/(1x).  Paul D. Hanna, Sep 03 2008
G.f.: 1/(12*xx^2/(14*x4*x^2/(16*x9*x^2/(18*x16*x^2/(110*x25*x^2/(1... (continued fraction);
G.f.: 1/(1xx/(1x/(1x2*x/(12*x/(1x3*x/(13*x/(1x4*x/(14*x/(1x5*x/(15*x/(1... (continued fraction).
(End)
O.g.f.: Sum_{n>=0} (n+2)^n*x^n/(1 + (n+1)*x)^(n+1).  Paul D. Hanna, Sep 19 2011
G.f. hypergeom([1,k],[],x/(1x))/(1x), for k=1,2,...,9 is the generating function for A000522, A001339, A082030, A095000, A095177, A096307, A096341, A095722, and A095740.  Mark van Hoeij, Nov 07 2011
G.f.: 1/U(0) where U(k) = 1  x  x*(k+1)/(1  x*(k+1)/U(k+1)); (continued fraction).  Sergei N. Gladkovskii, Oct 14 2012
E.g.f.: 1/U(0) where U(k) = 1  x/(1  1/(1 + (k+1)/U(k+1))); (continued fraction).  Sergei N. Gladkovskii, Nov 16 2012
G.f.: 1/(1x)/Q(0), where Q(k) = 1  x/(1x)*(k+1)/(1  x/(1x)*(k+1)/Q(k+1)); (continued fraction).  Sergei N. Gladkovskii, May 19 2013
G.f.: 2/(1x)/G(0), where G(k) = 1 + 1/(1  x*(2*k+2)/(x*(2*k+3)  1 + x*(2*k+2)/G(k+1))); (continued fraction).  Sergei N. Gladkovskii, May 31 2013
G.f.: (B(x)+ 1)/(22*x) = Q(0)/(22*x), where B(x) be g.f. A006183, Q(k) = 1 + 1/(1  x*(k+1)/(x*(k+1) + (1x)/Q(k+1) )); (continued fraction).  Sergei N. Gladkovskii, Aug 08 2013
G.f.: 1/Q(0), where Q(k) = 1  2*x*(k+1)  x^2*(k+1)^2/Q(k+1); (continued fraction).  Sergei N. Gladkovskii, Sep 30 2013
E.g.f.: e^x/(1x) = (1  12*x/(Q(0) + 6*x  3*x^2))/(1x), where Q(k) = 2*(4*k+1)*(32*k^2 + 16*k + x^2  6)  x^4*(4*k1)*(4*k+7)/Q(k+1); (continued fraction).  Sergei N. Gladkovskii, Nov 18 2013
G.f.: conjecture: T(0)/(12*x), where T(k) = 1  x^2*(k+1)^2/(x^2*(k+1)^2  (1  2*x*(k+1))*(1  2*x*(k+2))/T(k+1) ); (continued fraction).  Sergei N. Gladkovskii, Nov 18 2013
0 = a(n)*(+a(n+1)  3*a(n+2) + a(n+3)) + a(n+1)*(+a(n+1)  a(n+3)) + a(n+2)*(+a(n+2)) for all n>=0.  Michael Somos, Jul 04 2014
a(n) = F(n), where the function F(x) := Integral_{0..infinity} e^(u)*(1 + u)^x du smoothly interpolates this sequence to all real values of x. Note that F(1) = G and for n = 2,3,... we have F(n) = (1)^n/(n1)! *( A058006(n2)  G ), where G = 0.5963473623... denotes Gompertz's constant  see A073003.
a(n) = n!*e  e*( Sum_{k >= 0} (1)^k/((n + k + 1)*k!) ).
(End)
a(n) = (e/(2*Pi))*Integral_{x=oo..oo} (n+1+i*x)!/(1+i*x) dx.  David Ulgenes, Apr 18 2023


EXAMPLE

G.f. = 1 + 2*x + 5*x^2 + 16*x^3 + 65*x^4 + 326*x^5 + 1957*x^6 + 13700*x^7 + ...
With two objects we can form 5 sequences: (), (a), (b), (a,b), (b,a), so a(2) = 5.
The 16 arrangements of the 3set and their RGS (dots denote zeros) are
[ #] RGS perm. of subset
[ 1] [ . . . ] [ ]
[ 2] [ . . 1 ] [ 3 ]
[ 3] [ . 1 . ] [ 2 ]
[ 4] [ . 1 1 ] [ 2 3 ]
[ 5] [ . 1 2 ] [ 3 2 ]
[ 6] [ 1 . . ] [ 1 ]
[ 7] [ 1 . 1 ] [ 1 3 ]
[ 8] [ 1 . 2 ] [ 3 1 ]
[ 9] [ 1 1 . ] [ 1 2 ]
[10] [ 1 1 1 ] [ 1 2 3 ]
[11] [ 1 1 2 ] [ 1 3 2 ]
[12] [ 1 1 3 ] [ 2 3 1 ]
[13] [ 1 2 . ] [ 2 1 ]
[14] [ 1 2 1 ] [ 2 1 3 ]
[15] [ 1 2 2 ] [ 3 1 2 ]
[16] [ 1 2 3 ] [ 3 2 1 ]
(End)


MAPLE

a(n):= exp(1)*int(x^n*exp(x)*Heaviside(x1), x=0..infinity); # Karol A. Penson, Oct 01 2001
G(x):=exp(x)/(1x): f[0]:=G(x): for n from 1 to 26 do f[n]:=diff(f[n1], x) od: x:=0: seq(f[n], n=0..20);
G:=exp(z)/(1z): Gser:=series(G, z=0, 21):
for n from 0 to 20 do a(n):=n!*coeff(Gser, z, n): end do
k := 1; series(hypergeom([1, k], [], x/(1x))/(1x), x=0, 20); # Mark van Hoeij, Nov 07 2011
# one more Maple program:
a:= proc(n) option remember;
`if`(n<0, 0, 1+n*a(n1))
end:
seq(simplify(KummerU(n, n, 1)), n = 0..23); # Peter Luschny, May 10 2022


MATHEMATICA

Table[FunctionExpand[Gamma[n + 1, 1]*E], {n, 0, 24}]
nn = 20; Accumulate[Table[1/k!, {k, 0, nn}]] Range[0, nn]! (* Jan Mangaldan, Apr 21 2013 *)
FoldList[#1*#2 + #2 &, 0, Range@ 23] + 1 (* or *)
RecurrenceTable[{a[n + 1] == (n + 1) a[n] + 1, a[0] == 1}, a, {n, 0, 12}] (* Emanuele Munarini, Apr 27 2017 *)
nxt[{n_, a_}]:={n+1, a(n+1)+1}; NestList[nxt, {0, 1}, 30][[All, 2]] (* Harvey P. Dale, Jan 29 2023 *)


PROG

(PARI) {a(n) = local(A); if( n<0, 0, A = vector(n+1); A[1]=1; for(k=1, n, A[k+1] = k*A[k] + 1); A[n+1])}; /* Michael Somos, Jul 01 2004 */
(PARI) {a(n) = if( n<0, 0, n! * polcoeff( exp( x +x * O(x^n)) / (1  x), n))}; /* Michael Somos, Mar 06 2004 */
(PARI) a(n)=local(A=1+x+x*O(x^n)); for(i=1, n, A=1/(1x)^2+x^2*deriv(A)/(1x)); polcoeff(A, n) \\ Paul D. Hanna, Sep 03 2008
(PARI) {a(n)=local(X=x+x*O(x^n)); polcoeff(sum(m=0, n, (m+2)^m*x^m/(1+(m+1)*X)^(m+1)), n)} /* Paul D. Hanna */
(PARI) a(n)=sum(k=0, n, binomial(n, k)*k!); \\ Joerg Arndt, Dec 14 2014
(Haskell)
import Data.List (subsequences, permutations)
a000522 = length . choices . enumFromTo 1 where
choices = concat . map permutations . subsequences
(Sage)
@CachedFunction
def b(n, i, t):
if n <= 1:
return 1
return sum(b(n  1, j, t + (j == i)) for j in range(t + 2))
def a(n):
return b(n, 0, 0)
v000522 = [a(n) for n in range(33)]
print(v000522)
(Magma) [1] cat [n eq 1 select (n+1) else n*Self(n1)+1: n in [1..25]]; // Vincenzo Librandi, Feb 15 2015
(Maxima) a(n) := if n=0 then 1 else n*a(n1)+1; makelist(a(n), n, 0, 12); /* Emanuele Munarini, Apr 27 2017 */


CROSSREFS

Cf. A000166, A002627, A006231, A064383, A064384, A008290, A010844, A010845, A014508, A038159, A054091, A058006, A072453, A072456, A073591, A082030, A095000, A095177, A108625, A121579, A124779, A142992, A143007, A158359, A158821, A195254, A222637A222639, A038155, A000217.
Average of nth row of triangle in A007526.


KEYWORD

nonn,easy,nice


AUTHOR



EXTENSIONS



STATUS

approved



