E.g.f. -arctanh(cos(x)-cosh(x)), coefficients of (4*i+2) only.

A013478

E.g.f. -arctanh(cos(x)-cosh(x)), coefficients of (4*i+2) only.

Terms

    a(0) =2a(1) =242a(2) =735842a(3) =12696924242

External references