OFFSET
1,4
COMMENTS
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..420
FORMULA
a(n) ~ n! * n / (12 * (log(2))^(n-1)). - Vaclav Kotesovec, May 03 2015
MAPLE
b:= proc(n) option remember; `if`(n=0, [1, 0], add((p-> p+
[0, p[1]*binomial(j, 3)])(b(n-j))*binomial(n, j), j=1..n))
end:
a:= n-> b(n)[2]:
seq(a(n), n=1..25); # Alois P. Heinz, Dec 08 2014
MATHEMATICA
b[n_] := b[n] = If[n==0, {1, 0}, Sum[Function[p, p+{0, p[[1]]*Binomial[j, 3]} ][b[n-j]]*Binomial[n, j], {j, 1, n}]]; a[n_] := b[n][[2]]; Table[a[n], {n, 1, 25}] (* Jean-François Alcover, Feb 28 2017, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 13 2014
EXTENSIONS
a(8)-a(21) from Alois P. Heinz, Dec 08 2014
STATUS
approved