OFFSET
0,3
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 789
FORMULA
E.g.f.: log(-1/(-1+log(-1/(-1+x))^2)).
E.g.f.: -log(1-(log(1-x))^2). - Vaclav Kotesovec, Oct 01 2013
a(n) ~ (n-1)! * (exp(1)/(exp(1)-1))^n. - Vaclav Kotesovec, Oct 01 2013
MAPLE
spec := [S, {B=Cycle(Z), C=Prod(B, B), S=Cycle(C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
CoefficientList[Series[-Log[1-(Log[1-x])^2], {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Oct 01 2013 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
More terms from Alois P. Heinz, Mar 16 2016
STATUS
approved