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 A053529 a(n) = n! * number of partitions of n. 54
 1, 1, 4, 18, 120, 840, 7920, 75600, 887040, 10886400, 152409600, 2235340800, 36883123200, 628929100800, 11769069312000, 230150688768000, 4833164464128000, 105639166144512000, 2464913876705280000, 59606099200327680000, 1525429559126753280000, 40464026199993876480000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Commuting permutations: number of ordered pairs (g, h) in Sym(n) such that gh = hg. Equivalently sum of the order of all normalizers of all cyclic subgroups of Sym(n). - Olivier Gérard, Apr 04 2012 From Gus Wiseman, Jan 16 2019: (Start) Also the number of Young tableaux with distinct entries from 1 to n, where a Young tableau is an array obtained by replacing the dots in the Ferrers diagram of an integer partition of n with positive integers. For example, the a(3) = 18 tableaux are: 123 213 132 312 231 321 . 12 21 13 31 23 32 3 3 2 2 1 1 . 1 2 1 3 2 3 2 1 3 1 3 2 3 3 2 2 1 1 (End) REFERENCES R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.12, solution. LINKS T. D. Noe, Table of n, a(n) for n = 0..200 M. Holloway, M. Shattuck, Commuting pairs of functions on a finite set, PU.M.A, Volume 24 (2013), Issue No. 1. M. Holloway, M. Shattuck, Commuting pairs of functions on a finite set, Research Gate, 2015. R. P. Stanley, Pairs with equal squares, Problem 10654, Amer. Math. Monthly, 107 (April 2000), solution p. 368. Wikipedia, Young tableau FORMULA E.g.f: Sum_{n>=0} x^n/(Product_{k=1..n} 1-x^k) = exp(Sum_{n>=1} (x^n/n)/(1-x^n))). - Joerg Arndt, Jan 29 2011 a(n) = Sum{k=1..n} (((n-1)!/(n-k)!)*sigma(k)*a(n-k)), n > 0, and a(0)=1. See A274760. - Johannes W. Meijer, Jul 28 2016 a(n) ~ sqrt(Pi/6)*exp(sqrt(2/3)*Pi*sqrt(n))*n^n/(2*exp(n)*sqrt(n)). - Ilya Gutkovskiy, Jul 28 2016 MAPLE seq(count(Permutation(n))*count(Partition(n)), n=1..20); # Zerinvary Lajos, Oct 16 2006 with(combinat): A053529 := proc(n): n! * numbpart(n) end: seq(A053529(n), n=0..20); # Johannes W. Meijer, Jul 28 2016 MATHEMATICA Table[PartitionsP[n] n!, {n, 0, 20}] (* T. D. Noe, Jun 19 2012 *) PROG (PARI) N=66; x='x+O('x^N); Vec(serlaplace(exp(sum(k=1, N, x^k/(1-x^k)/k)))) \\ Joerg Arndt, Apr 16 2010 (PARI) N=66; x='x+O('x^N); Vec(serlaplace(sum(n=0, N, x^n/prod(k=1, n, 1-x^k)))) \\ Joerg Arndt, Jan 29 2011 (PARI) a(n) = n!*numbpart(n); \\ Michel Marcus, Jul 28 2016 (Magma) a:= func< n | NumberOfPartitions(n)*Factorial(n) >; [ a(n) : n in [0..25]]; // Vincenzo Librandi, Jan 17 2019 (Python) from math import factorial from sympy import npartitions def A053529(n): return factorial(n)*npartitions(n) # Chai Wah Wu, Jul 10 2023 CROSSREFS Column k=2 of A362827. Cf. A000041, A072169, A061256. Sequences counting pairs of functions from an n-set to itself: A053529, A181162, A239749-A239785, A239836-A239841. Cf. A000085, A117433, A153452, A296188, A323295, A323434, A323436. Sequence in context: A321704 A296982 A222375 * A005442 A306881 A367489 Adjacent sequences: A053526 A053527 A053528 * A053530 A053531 A053532 KEYWORD nonn,easy,nice AUTHOR N. J. A. Sloane, Jan 16 2000 STATUS approved

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