A052864 E.g.f.: (log(1-x))^2/(1+log(1-x)).

0, 0, 2, 12, 82, 670, 6458, 72072, 915864, 13068768, 206998032, 3604604256, 68455569840, 1408152976464, 31191374639280, 740216664633984, 18736923967232256, 503916672279712896, 14349543617967990912

Offset

0,3

Comments

Previous name was: A simple grammar.

Links

Table of n, a(n) for n=0..18.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 832

Formula

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

a(n) ~ n! * exp(n)/(exp(1)-1)^(n+1). - Vaclav Kotesovec, Oct 01 2013

Maple

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

Mathematica

CoefficientList[Series[(Log[1-x])^2/(1+Log[1-x]), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Oct 01 2013 *)

Crossrefs

Cf. A009122.

Sequence in context: A092850 A199420 A235348 * A355378 A136278 A130464

Adjacent sequences: A052861 A052862 A052863 * A052865 A052866 A052867

Keyword

easy,nonn

Author

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

Extensions

New name using e.g.f., Vaclav Kotesovec, Oct 01 2013

Status

approved