OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..60
MAPLE
h:= l-> (n-> mul(mul(1+l[i]-j+add(`if`(l[k]>=j, 1, 0),
k=i+1..n), j=1..l[i]), i=1..n))(nops(l)):
g:= (n, i, l)-> `if`(n=0 or i=1, h([l[], 1$n]), `if`(i<1, 0,
`if`(i>n, 0, g(n-i, i, [l[], i]))+g(n, i-1, l))):
a:= n-> g(n$2, []):
seq(a(n), n=0..22); # Alois P. Heinz, Nov 05 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Wolfdieter Lang, Oct 08 2015
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Nov 05 2015
STATUS
approved