OFFSET
0,3
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 801
FORMULA
E.g.f.: exp(exp(x)-1)*exp(x)-exp(x)-exp(exp(x)-1)+1.
a(n) = A005493(n-1)-1. - R. J. Mathar, Jun 03 2022
MAPLE
spec := [S, {B=Set(Z, 1 <= card), C=Set(B, 1 <= card), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
Join[{0}, (#[[2]]-#[[1]]&/@Partition[BellB[Range[30]], 2, 1])-1] (* Harvey P. Dale, May 31 2015 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
Better description from Vladeta Jovovic, Jul 24 2003
More terms from Alois P. Heinz, Mar 16 2016
STATUS
approved