Expansion of e.g.f.: 1/cos(sinh(x)) (even-indexed coefficients only).

A009009

Expansion of e.g.f.: 1/cos(sinh(x)) (even-indexed coefficients only).

Terms

    a(0) =1a(1) =1a(2) =9a(3) =177a(4) =6545a(5) =387649a(6) =33646041a(7) =4025701617a(8) =635120351777

External references