OFFSET
1,5
FORMULA
a(n)=n!*b(n), b(n)=1/(n*(n-1)*(n-2))*(i=1..n-4, b(n-3)+sum(b(i)*b(n-3-i))), n>3, b(1)=1, b(2)=1/2, b(3)=1/6.
PROG
(Maxima)
a(n):=if n<4 then 1/n! else 1/(n*(n-1)*(n-2))*(a(n-3)+sum(a(i)*a(n-3-i), i, 1, n-4));
makelist(n!*a3(n), n, 1, 25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Kruchinin, Nov 18 2011
STATUS
approved