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 A002627 a(n) = n*a(n-1) + 1, a(0) = 0. (Formerly M2858 N1149) 43
 0, 1, 3, 10, 41, 206, 1237, 8660, 69281, 623530, 6235301, 68588312, 823059745, 10699776686, 149796873605, 2246953104076, 35951249665217, 611171244308690, 11001082397556421, 209020565553572000, 4180411311071440001, 87788637532500240022 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS This sequence shares divisibility properties with A000522; each of the primes in A072456 divide only a finite number of terms of this sequence. - T. D. Noe, Jul 07 2005 Sum of the lengths of the first runs in all permutations of [n]. Example: a(3)=10 because the lengths of the first runs in the permutation (123),(13)2,(3)12,(2)13,(23)1 and (3)21 are 3,2,1,1,2 and 1, respectively (first runs are enclosed between parentheses). Number of cells in the last columns of all deco polyominoes of height n. A deco polyomino is a directed column-convex polyomino in which the height, measured along the diagonal, is attained only in the last column. a(n) = Sum_{k=1..n} k*A092582(n,k). - Emeric Deutsch, Aug 16 2006 Starting with offset 1 = eigensequence of an infinite lower triangular matrix with (1, 2, 3, ...) as the right border, (1, 1, 1, ...) as the left border, and the rest zeros. - Gary W. Adamson, Apr 27 2009 Sums of rows of the triangle in A173333, n > 0. - Reinhard Zumkeller, Feb 19 2010 if s(n) is a sequence defined as s(0) = x, s(n) = n*s(n-1)+k, n > 0 then s(n) = n!*x + a(n)*k. - Gary Detlefs, Feb 20 2010 Number of arrangements of proper subsets of n distinct objects, i.e., arrangements which are not permutations (where the empty set is considered a proper subset of any nonempty set); see example. - Daniel Forgues, Apr 23 2011 For n >= 0, A002627(n+1) is the sequence of sums of Pascal-like triangle with one side 1,1,..., and the other side A000522. - Vladimir Shevelev, Feb 06 2012 a(n) = q(n,1) for n >= 1, where the polynomials q are defined at A248669. - Clark Kimberling, Oct 11 2014 a(n) is the number of quasilinear weak orderings on {1,...,n}. - J. Devillet, Dec 22 2017 REFERENCES D. Singh, The numbers L(m,n) and their relations with prepared Bernoulli and Eulerian numbers, Math. Student, 20 (1952), 66-70. 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 Seiichi Manyama, Table of n, a(n) for n = 0..449 (terms 0..100 from T. D. Noe) Sanka Balasuriya, Igor E. Shparlinski and Arne Winterhof, An average bound for character sums with some counter-dependent recurrence sequences, Rocky Mt. J. Math. 39, No. 5, 1403-1409 (2009). E. Barcucci, A. Del Lungo and R. Pinzani, "Deco" polyominoes, permutations and random generation, Theoretical Computer Science, 159, 1996, 29-42. Jonathan Beagley and Lara Pudwell, Colorful Tilings and Permutations, Journal of Integer Sequences, Vol. 24 (2021), Article 21.10.4. J. Devillet, Bisymmetric and quasitrivial operations: characterizations and enumerations, [math.RA] arXiv:1712.07856 (2017). INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 150 D. Singh, The numbers L(m,n) and their relations with prepared Bernoulli and Eulerian numbers, Math. Student, 20 (1952), 66-70. [Annotated scanned copy] Jun Yan, Results on pattern avoidance in parking functions, arXiv:2404.07958 [math.CO], 2024. See p. 5. FORMULA a(n) = n! * Sum_{k=1..n} 1/k!. a(n) = A000522(n) - n!. - Michael Somos, Mar 26 1999 a(n) = floor( n! * (e-1) ), n >= 1. - Amarnath Murthy, Mar 08 2002 E.g.f.: (exp(x)-1)/(1-x). - Mario Catalani (mario.catalani(AT)unito.it), Feb 06 2003 Binomial transform of A002467. - Ross La Haye, Sep 21 2004 a(n) = Sum_{j=1..n} (n-j)!*binomial(n,j). - Zerinvary Lajos, Jul 31 2006 a(n) = 1 + Sum_{k=0..n-1} k*a(k). - Benoit Cloitre, Jul 26 2008 a(m) = int(((1+s)^m - s^m)*exp(-s), s=0..infinity) = GAMMA(m+1,1) * exp(1) - GAMMA(m+1). - Stephen Crowley, Jul 24 2009 From Sergei N. Gladkovskii, Jul 05 2012: (Start) a(n+1) = A000522(n) + A001339(n) - A000142(n+1); E.g.f.: Q(0)/(1-x), where Q(k)= 1 + (x-1)*k!/(1 - x/(x + (x-1)*(k+1)!/Q(k+1))); (continued fraction). (End) E.g.f.: x/(1-x)*E(0)/2, where E(k)= 1 + 1/(1 - x/(x + (k+2)/E(k+1))); (continued fraction). - Sergei N. Gladkovskii, Jun 01 2013 1/(e - 1) = 1 - 1!/(1*3) - 2!/(3*10) - 3!/(10*41) - 4!/(41*206) - ... (see A056542 and A185108). - Peter Bala, Oct 09 2013 Conjecture: a(n) + (-n-1)*a(n-1) + (n-1)*a(n-2) = 0. - R. J. Mathar, Feb 16 2014 The e.g.f. f(x) = (exp(x)-1)/(1-x) satisfies the differential equation: (1-x)*f'(x) - (2-x)*f(x) + 1, from which we can obtain the recurrence: a(n+1) = a(n) + n! + Sum_{k=1..n} (n!/k!)*a(k). The above conjectured recurrence can be obtained from the original recurrence or from the differential equation satisfied by f(x). - Emanuele Munarini, Jun 20 2014 Limit_{n -> infinity} a(n)/n! = exp(1) - 1. - Carmine Suriano, Jul 01 2015 Product_{n>=2} a(n)/(a(n)-1) = exp(1) - 1. See A091131. - James R. Buddenhagen, Jul 21 2019 EXAMPLE [a(0), a(1), ...] = GAMMA(m+1,1)*exp(1) - GAMMA(m+1) = [exp(-1)*exp(1)-1, 2*exp(-1)*exp(1)-1, 5*exp(-1)*exp(1)-2, 16*exp(-1)*exp(1)-6, 65*exp(-1)*exp(1)-24, 326*exp(-1)*exp(1)-120, ...]. - Stephen Crowley, Jul 24 2009 From Daniel Forgues, Apr 25 2011: (Start) n=0: {}: #{} = 0 n=1: {1}: #{()} = 1 n=2: {1,2}: #{(),(1),(2)} = 3 n=3: {1,2,3}: #{(),(1),(2),(3),(1,2),(2,1),(1,3),(3,1),(2,3),(3,2)} = 10 (End) x + 3*x^2 + 10*x^3 + 41*x^4 + 206*x^5 + 1237*x^6 + 8660*x^7 + 69281*x^8 + ... MAPLE A002627 := proc(n) add( (n-j)!*binomial(n, j), j=1..n) ; end proc: seq(A002627(n), n=0..21) ; # Zerinvary Lajos, Jul 31 2006 MATHEMATICA FoldList[ #1*#2 + 1 &, 0, Range[21]] (* Robert G. Wilson v, Oct 11 2005 *) RecurrenceTable[{a[0]==0, a[n]==n*a[n-1]+1}, a, {n, 30}] (* Harvey P. Dale, Mar 29 2015 *) PROG (PARI) a(n)= n!*sum(k=1, n, 1/k!); \\ Joerg Arndt, Apr 24 2011 (Haskell) a002627 n = a002627_list !! n a002627_list = 0 : map (+ 1) (zipWith (*) [1..] a002627_list) -- Reinhard Zumkeller, Mar 24 2013 (Maxima) makelist(sum(n!/k!, k, 1, n), n, 0, 40); /* Emanuele Munarini, Jun 20 2014 */ (Magma) I:=[1]; [0] cat [n le 1 select I[n] else n*Self(n-1)+1:n in [1..21]]; // Marius A. Burtea, Aug 07 2019 CROSSREFS Cf. A000522, A001113, A092582. Second diagonal of A059922, cf. A056542. Conjectured to give records in A130147. Sequence in context: A245504 A305405 A030927 * A030802 A030942 A030855 Adjacent sequences: A002624 A002625 A002626 * A002628 A002629 A002630 KEYWORD nonn,easy,nice,changed AUTHOR N. J. A. Sloane EXTENSIONS Comments from Michael Somos STATUS approved

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Last modified April 19 12:14 EDT 2024. Contains 371792 sequences. (Running on oeis4.)