the Odlyzko reference. a(n) is asymptotic to b^n*exp(b-n-1/2)/sqrt(ln(n)) where b satisfies b*ln(b) = n - 1/2 (see Graham, Knuth and Patashnik, Concrete Mathematics, 2nd ed., p. 493) - Benoit Cloitre (abcloitre(AT)wanadoo.fr), Oct 23 2002 Maple: A000110:= (0)

by g
Venue:version 1 A:=series(exp(exp(x)-1),x,60); A000110:=n->n!*coeff(A,x,n); # version 2 with(combstruct); spec:=[S, {S=Set(U,card >= 1), U=Set(Z, card >= 1)},labeled]; [seq(combstruct[count](spec, size=n), n=0..40)]; Math'ca: f[n_] := Sum[ StirlingS2[n, k], {k,