tanh(sec(x)*arctan(x))=x-1/3!*x^3+25/5!*x^5-1209/7!*x^7+68945/9!*x^9...

A012809

tanh(sec(x)*arctan(x))=x-1/3!*x^3+25/5!*x^5-1209/7!*x^7+68945/9!*x^9...

Terms

    a(0) =1a(1) =-1a(2) =25a(3) =-1209a(4) =68945a(5) =-7692881a(6) =1181481769a(7) =-242740782153

External references