A052597 E.g.f. 1/(1-x^2-x^3).

1, 0, 2, 6, 24, 240, 1440, 15120, 161280, 1814400, 25401600, 359251200, 5748019200, 99632332800, 1830744115200, 36614882304000, 774143225856000, 17428683976704000, 416154290872320000, 10461478635159552000

Offset

0,3

Links

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 542

Formula

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

Recurrence: {a(1)=0, a(0)=1, a(2)=2, (-11*n-6-n^3-6*n^2)*a(n) +(-n^2-5*n-6)*a(n+1) +a(n+3)=0}

Sum(-1/23*(-3-7*_alpha+2*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(_Z^3+_Z^2-1))*n!

a(n) = n!*A000931(n+3). - R. J. Mathar, Nov 27 2011

Maple

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

Mathematica

With[{nn=20}, CoefficientList[Series[1/(1-x^2-x^3), {x, 0, nn}], x] Range[ 0, nn]!] (* Harvey P. Dale, Oct 18 2013 *)

Crossrefs

Sequence in context: A074351 A352060 A346121 * A052632 A052692 A052723

Adjacent sequences: A052594 A052595 A052596 * A052598 A052599 A052600

Keyword

easy,nonn

Author

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

Status

approved