Expansion of tanh(tan(x))/cos(x).

A009813

Expansion of tanh(tan(x))/cos(x).

Terms

    a(0) =1a(1) =3a(2) =17a(3) =147a(4) =3265a(5) =248259a(6) =25402769a(7) =2697740307a(8) =299763466753

External references