E.g.f.: sech(sin(arctan(x))) (even powers only).

A012029

E.g.f.: sech(sin(arctan(x))) (even powers only).

Terms

    a(0) =1a(1) =-1a(2) =17a(3) =-721a(4) =56993a(5) =-7232161a(6) =1344866225a(7) =-344599447921

External references