A052832 A simple grammar.

0, 0, 2, 6, 36, 240, 2040, 20160, 231840, 3024000, 44271360, 718502400, 12813292800, 249080832000, 5243151513600, 118824010905600, 2884729655808000, 74694359900160000, 2054806272110592000, 59849389401145344000, 1840003788783992832000, 59545276650123264000000

Offset

0,3

Links

Table of n, a(n) for n=0..21.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 797

Formula

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

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

(RootOf(_Z^2-_Z-1)^n*RootOf(_Z^2-_Z-1)+(1-RootOf(_Z^2-_Z-1))^(n+1)-1)*GAMMA(n+1)/RootOf(_Z^2-_Z-1)/(-1+RootOf(_Z^2-_Z-1)).

Maple

spec := [S, {B=Prod(Z, C), C=Sequence(Z, 1 <= card), S= Cycle(B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);

Crossrefs

Sequence in context: A002869 A293120 A052845 * A058583 A345747 A075096

Adjacent sequences: A052829 A052830 A052831 * A052833 A052834 A052835

Keyword

easy,nonn

Author

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

Extensions

More terms from Alois P. Heinz, Mar 16 2016

Status

approved