OFFSET
0,6
FORMULA
a(n)=sum(k=1..n, binomial(n-k-1,k-1)*a(k-1)), a(0)=1.
PROG
(Maxima)
a(n):=if n=0 then 1 else sum(binomial(n-k-1, k-1)*a(k-1), k, 1, n);
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Kruchinin, Nov 28 2011
STATUS
approved