A052628 Expansion of e.g.f. (2+x^3-x^4)/(1-x).

2, 2, 4, 18, 48, 240, 1440, 10080, 80640, 725760, 7257600, 79833600, 958003200, 12454041600, 174356582400, 2615348736000, 41845579776000, 711374856192000, 12804747411456000, 243290200817664000

Offset

0,1

Links

Table of n, a(n) for n=0..19.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 574

Formula

E.g.f.: (-2+x^4-x^3)/(-1+x).

Recurrence: {(-1-n)*a(n)+a(n+1)=0, a(2)=4, a(1)=2, a(0)=2, a(4)=48, a(3)=18}

2*n!, n != 3.

Maple

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

Mathematica

With[{nn=20}, CoefficientList[Series[(2+x^3-x^4)/(1-x), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Feb 03 2015 *)

Crossrefs

Sequence in context: A376085 A232161 A335684 * A390857 A006853 A120417

Adjacent sequences: A052625 A052626 A052627 * A052629 A052630 A052631

Keyword

easy,nonn

Author

INRIA Encyclopedia of Combinatorial Structures, Jan 25 2000

Status

approved