a(n) = Sum_{k=0..n-1} (-1)^(k)*C(n-1,k)*a(n-1-k)*a(k) for n>0 with a(0)=1.
1, 1, 0, 2, 0, 16, 0, 272, 0, 7936, 0, 353792, 0, 22368256, 0, 1903757312, 0
2 seqfan posts
Tue Nov 10 10:51:14 CET 2009 [seqfan] Re: Surprising Patterns in Tangent and Secant Numbers