OFFSET
0,3
COMMENTS
Previous name was: A simple grammar.
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 814
FORMULA
E.g.f.: log(-1/(-2+exp(x)))*exp(x)-log(-1/(-2+exp(x)))
a(n) ~ (n-1)! / log(2)^n. - Vaclav Kotesovec, Sep 30 2013
MAPLE
spec := [S, {B=Set(Z, 1 <= card), C=Cycle(B), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
CoefficientList[Series[(1-E^x) * Log[2-E^x], {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Sep 30 2013 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
New name, using e.g.f., by Vaclav Kotesovec, Sep 30 2013
STATUS
approved