A052635 E.g.f. (1-3x)/(1-3x-x^2).

1, 0, 2, 18, 240, 3960, 78480, 1814400, 47940480, 1425029760, 47065536000, 1709915961600, 67769625369600, 2909762279424000, 134544087553075200, 6665534018567424000, 352236213903974400000, 19777072162153033728000

Offset

0,3

Links

Table of n, a(n) for n=0..17.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 581

Formula

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

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

Sum(1/13*(-3+11*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+3*_Z+_Z^2))*n!

a(n)=n!*A006190(n-1). - R. J. Mathar, Jun 03 2022

Maple

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

Crossrefs

Sequence in context: A364167 A357603 A024486 * A366001 A259270 A168562

Adjacent sequences: A052632 A052633 A052634 * A052636 A052637 A052638

Keyword

easy,nonn

Author

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

Status

approved