OFFSET
1,5
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..200
FORMULA
a(n)=3^(n-1)*n!*T(n,1), T(n,m)=1/3*(stirling2(n,m)*m!/n!-sum(k=m+1..n-1, T(k,m)*sum(i=k..n, T(n,i)*T(i,k)))-T(m,m)*sum(i=m+1..n-1, T(n,i)*T(i,m))), n>m, T(n,n)=1.
PROG
(Maxima)
T(n, m):=if n=m then 1 else 1/3*(stirling2(n, m)*m!/n!-sum(T(k, m)*sum(T(n, i)*T(i, k), i, k, n), k, m+1, n-1)-T(m, m)*sum(T(n, i)*T(i, m), i, m+1, n-1));
makelist(n!*3^(n-1)*(T(n, 1)), n, 1, 7);
CROSSREFS
KEYWORD
sign
AUTHOR
Vladimir Kruchinin, Mar 10 2012
STATUS
approved