A052590 E.g.f. (1-x)/(1-4x+2x^2).

1, 3, 20, 204, 2784, 47520, 973440, 23264640, 635443200, 19525847040, 666654105600, 25037094297600, 1025783842406400, 45529186384281600, 2176249118883840000, 111452688851632128000, 6088372509440212992000

Offset

0,2

Links

Table of n, a(n) for n=0..16.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 535

Formula

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

Recurrence: {a(0)=1, a(1)=3, (2*n^2+6*n+4)*a(n)+(-4*n-8)*a(n+1)+a(n+2)=0}

Sum(1/4*_alpha^(-1-n), _alpha=RootOf(1-4*_Z+2*_Z^2))*n!

a(n) =n!*A007052(n). - R. J. Mathar, Nov 27 2011

Maple

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

Mathematica

With[{nn=20}, CoefficientList[Series[(1-x)/(1-4x+2x^2), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jan 10 2014 *)

Crossrefs

Sequence in context: A244491 A295100 A367922 * A081209 A196560 A257476

Adjacent sequences: A052587 A052588 A052589 * A052591 A052592 A052593

Keyword

easy,nonn

Author

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

Status

approved