

A052832


A simple grammar.


0



0, 0, 2, 6, 36, 240, 2040, 20160, 231840, 3024000, 44271360, 718502400, 12813292800, 249080832000, 5243151513600, 118824010905600, 2884729655808000, 74694359900160000, 2054806272110592000, 59849389401145344000, 1840003788783992832000, 59545276650123264000000
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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)+(42*n)*a(n+2)+a(n+3)}.
(RootOf(_Z^2_Z1)^n*RootOf(_Z^2_Z1)+(1RootOf(_Z^2_Z1))^(n+1)1)*GAMMA(n+1)/RootOf(_Z^2_Z1)/(1+RootOf(_Z^2_Z1)).


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 A052845 A293120 * A058583 A075096 A177373
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



