OFFSET
0,3
FORMULA
a(n) = n!^2*sum(m=1..n, (2^(n-2*m)*(-1)^((n-m)/2)*sum(l=0..m, (2^l*l! *C(m,l)* sum(k=0..n-2*m+l, (k!*stirling1(l+k,l)*stirling2(n-2*m+l,k))/ ((l+k)!*(n-2*m+l)!)))))), a(0)=1.
PROG
(Maxima) a(n):=if n=0 then 1 else n!^2*sum((2^(n-2*m)*(-1)^((n-m)/2) *sum((2^l*l! *binomial(m, l)* sum((k!*stirling1(l+k, l)*stirling2(n-2 *m+l, k))/((l+k)!*(n-2*m+l)!), k, 0, n-2*m+l)), l, 0, m)), m, 1, n);
CROSSREFS
KEYWORD
sign
AUTHOR
Vladimir Kruchinin, Nov 07 2011
STATUS
approved