G.f. A(x) satisfies the condition that both A(x) and F(x) = A(x*F(x)) = o.g.f. of A157310 have zeros for every other coefficient after initial terms; g.f. of dual sequence A157308 satisfies the same condition.
1, 1, 0, 1, 0, 9, 0, 176, 0, 5693, 0, 272185, 0, 18043492, 0, 1587355800, 0
2 seqfan posts
Tue Nov 10 10:51:14 CET 2009 [seqfan] Re: Surprising Patterns in Tangent and Secant Numbers