E.g.f. 1/2*sqrt(sec(2*x))-1/2, (even part).

A217582

E.g.f. 1/2*sqrt(sec(2*x))-1/2, (even part).

Terms

    a(0) =0a(1) =1a(2) =14a(3) =556a(4) =43784a(5) =5723536a(6) =1119636704a(7) =306179943616

External references