

A033312


a(n) = n!  1.
(Formerly N1614)


80



0, 0, 1, 5, 23, 119, 719, 5039, 40319, 362879, 3628799, 39916799, 479001599, 6227020799, 87178291199, 1307674367999, 20922789887999, 355687428095999, 6402373705727999, 121645100408831999, 2432902008176639999
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OFFSET

0,4


COMMENTS

a(n) gives the index number in any table of permutations of the entry in which the last n + 1 items are reversed.  Eugene McDonnell (eemcd(AT)mac.com), Dec 03 2004
a(n), n >= 1, has the factorial representation [n  1, n  2, ..., 1, 0]. The (unique) factorial representation of a number m from {0, 1, ... n!  1} is m = sum(m_j(n)*j!, j = 0 .. n  1) with m_j(n) from {0, 1, .., j}, n>=1. This is encoded as [m_{n1},m_{n2},...,m+1,m_0] with m_0=0. This can be interpreted as (D. N.) Lehmer code for the lexicographic rank of permutations of the symmetric group S_n (see the W. Lang link under A136663). The Lehmer code [n  1, n  2, ..., 1, 0] stands for the permutation [n, n  1, ..., 1] (the last in lexicographic order).  Wolfdieter Lang, May 21 2008
For n >= 3: a(n) = numbers m for which there is one iteration {floor (r / k)} for k = n, n  1, n  2, ... 2 with property r mod k = k  1 starting at r = m. For n = 5: a(5) = 119; floor (119 / 5) = 23, 119 mod 5 = 4; floor (23 / 4) = 5, 23 mod 4 = 3; floor (5 / 3) = 1, 5 mod 3 = 2; floor (1 / 2) = 0; 1 mod 2 = 1.  Jaroslav Krizek, Jan 23 2010
For n = 4, define the sum of all possible products of 1, 2, 3, 4 to be 1 + 2 + 3 + 4 add 1*2 + 1*3 + 1*4 add 2*3 + 2*4 + 3*4 add 1*2*3 + 1*2*4 + 1*3*4 + 2*3*4 add 1*2*3*4. The sum of this is 119 = (4 + 1)!  1. For n = 5 I get the sum 719 = (5 + 1)!  1. The proof for the general case seems to follow by induction.  J. M. Bergot, Jan 10 2011


REFERENCES

A. T. Benjamin and J. J. Quinn, Proofs that really count: the art of combinatorial proof, M.A.A. 2003, id. 181.
Problem 598, J. Rec. Math., 11 (1978), 6869.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..300
S. Legendre, P. Paclet, On the Permutations Generated by Cyclic Shift , J. Int. Seq. 14 (2011) # 11.3.2
G. P. Michon, Wilson's Theorem
Hisanori Mishima, Factorizations of many number sequences
Hisanori Mishima, Factorizations of many number sequences
Andrew Walker, Factors of n! + 1
Eric Weisstein's World of Mathematics, Factorial
Eric Weisstein's World of Mathematics, Permutation Pattern
Index entries for sequences related to factorial numbers


FORMULA

a(n) = Sum_{k = 1 .. n} (k1)*(k1)!.
a(n) = a(n  1)*(n  1) + a(n  1) + n  1, a(0) = 0.  Reinhard Zumkeller, Feb 03 2003
a(0) = a(1) = 0, a(n) = a(n  1) * n + (n  1) for n >= 2.  Jaroslav Krizek, Jan 23 2010
E.g.f.: 1/(1  x)  exp(x).  Sergei N. Gladkovskii, Jun 29 2012
0 = 1 + a(n)*(+a(n+1)  a(n+2)) + a(n+1)*(+3 + a(n+1)) + a(n+2)*(1) for n>=0.  Michael Somos, Feb 24 2017


EXAMPLE

G.f. = x^2 + 5*x^3 + 23*x^4 + 119*x^5 + 719*x^6 + 5039*x^7 + 40319*x^8 + ...


MATHEMATICA

FoldList[#1*#2 + #2  1 &, 0, Range[19]] (* Robert G. Wilson v, Jul 07 2012 *)
Range[0, 19]!  1 (* Alonso del Arte, Jan 24 2013 *)


PROG

(PARI) a(n)=n!1 \\ Charles R Greathouse IV, Jul 19 2011
(MAGMA) [Factorial(n)1: n in [0..25]]; // Vincenzo Librandi, Jul 20 2011
(Maxima) A033312(n):= n!1$
makelist(A033312(n), n, 0, 30); /* Martin Ettl, Nov 03 2012 */


CROSSREFS

Cf. A000142, A001563 (first differences), A002582, A002982, A038507 (factorizations), A054415, A056110.
Sequence in context: A193704 A294356 A162815 * A151881 A229811 A121636
Adjacent sequences: A033309 A033310 A033311 * A033313 A033314 A033315


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane. This sequence appeared in the 1973 "Handbook", but was then dropped from the database. Resubmitted by Eric W. Weisstein. Entry revised by N. J. A. Sloane, Jun 12 2012


STATUS

approved



