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A052673 3*n*n!. 2
0, 3, 12, 54, 288, 1800, 12960, 105840, 967680, 9797760, 108864000, 1317254400, 17244057600, 242853811200, 3661488230400, 58845346560000, 1004293914624000, 18140058832896000, 345728180109312000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..18.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 621

Luis Manuel Rivera, Integer sequences and k-commuting permutations, arXiv preprint arXiv:1406.3081, 2014

FORMULA

E.g.f.: 3*x/(-1+x)^2

Recurrence: {a(0)=0, a(1)=3, (-n^2-2*n-1)*a(n)+a(n+1)*n =0}

3*n*n!

a(n) = A122972(n+2) - A122972(n) for n > 0. - Reinhard Zumkeller, Sep 21 2006

For n>0: a(n) = A083746(n+2). - Reinhard Zumkeller, Apr 14 2007

MAPLE

spec := [S, {S=Prod(Sequence(Z), Sequence(Z), Union(Z, Z, Z))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);

MATHEMATICA

Table[3 n n!, {n, 0, 20}] (* Harvey P. Dale, Feb 12 2017 *)

CROSSREFS

Sequence in context: A263853 A266083 A245374 * A180589 A042971 A256142

Adjacent sequences:  A052670 A052671 A052672 * A052674 A052675 A052676

KEYWORD

easy,nonn

AUTHOR

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

STATUS

approved

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Last modified September 22 03:54 EDT 2020. Contains 337289 sequences. (Running on oeis4.)