OFFSET
0,3
FORMULA
a(n)=2*sum(m=1..n, sum(r=0..(n-m)/2, (stirling1(n-m-2*r,m)*sum(i=0..(n/2-r),(2*i-n+2*r)^n*binomial(n-2*r,i)*(-1)^(n-r-i))/(2^(n-2*r)*(n-m-2*r)!)))), n>0, a(0)=1.
PROG
(Maxima)
a(n):=2*sum(sum((stirling1(n-m-2*r, m)*sum((2*i-n+2*r)^n*binomial(n-2*r, i)*(-1)^(n-r-i), i, 0, (n/2-r))/(2^(n-2*r)*(n-m-2*r)!)), r, 0, (n-m)/2), m, 1, n);
CROSSREFS
KEYWORD
sign
AUTHOR
Vladimir Kruchinin, Jun 03 2011
STATUS
approved