A052578 a(0) = 0, a(n) = 4*n! for n > 0.

0, 4, 8, 24, 96, 480, 2880, 20160, 161280, 1451520, 14515200, 159667200, 1916006400, 24908083200, 348713164800, 5230697472000, 83691159552000, 1422749712384000, 25609494822912000, 486580401635328000, 9731608032706560000, 204363768686837760000

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..447

Luis Manuel Rivera, Integer sequences and k-commuting permutations, arXiv preprint arXiv:1406.3081 [math.CO], 2014-2015.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 522

Formula

E.g.f.: -4*x/(-1+x)

Recurrence: {a(0)=0, (-1-n)*a(n)+a(n+1), a(1)=4}

Maple

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

Mathematica

Join[{0}, 4Range[25]!]  (* Harvey P. Dale, Mar 12 2011 *)

Prog

(PARI) a(n)=if(n, 4*n!, 0) \\ Charles R Greathouse IV, Nov 20 2011
(Magma) [0] cat [4*Factorial(n): n in [1..25]]; // Vincenzo Librandi, Feb 13 2018

Crossrefs

Cf. A000142, A052849 (k=2), A052560 (k=3).

Sequence in context: A008950 A045881 A303989 * A066631 A090896 A131637

Adjacent sequences: A052575 A052576 A052577 * A052579 A052580 A052581

Keyword

easy,nonn

Author

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

Status

approved