sech(sec(x)*tanh(x))=1-1/2!*x^2+1/4!*x^4-97/6!*x^6+2945/8!*x^8...

A012839

sech(sec(x)*tanh(x))=1-1/2!*x^2+1/4!*x^4-97/6!*x^6+2945/8!*x^8...

Terms

    a(0) =1a(1) =-1a(2) =1a(3) =-97a(4) =2945a(5) =-148929a(6) =15801729a(7) =-1624918817a(8) =267458400513

External references