OFFSET
0,3
COMMENTS
All terms are even.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..424
FORMULA
a(n) ~ n! / (2 * (log(2))^(n+1)). - Vaclav Kotesovec, Nov 27 2017
MAPLE
g:= proc(n) option remember; `if`(n<2, 1,
add(binomial(n, k)*g(k), k=0..n-1))
end:
b:= proc(n, i) option remember; `if`(n=0, 0, add(
`if`(i=j, g(n-j), b(n-j, j))*binomial(n, j), j=1..n))
end:
a:= n-> b(n, 0):
seq(a(n), n=0..25);
MATHEMATICA
g[n_] := g[n] = If[n<2, 1, Sum[Binomial[n, k]*g[k], {k, 0, n-1}]]; b[n_, i_] := b[n, i] = If[n==0, 0, Sum[If[i==j, g[n-j], b[n-j, j]]*Binomial[n, j], {j, 1, n}]]; a[n_] := b[n, 0]; Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Feb 15 2017, translated from Maple *)
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Sep 09 2015
STATUS
approved