tanh(sec(x)*arctanh(x))=x+3/3!*x^3-15/5!*x^5-1869/7!*x^7-88959/9!*x^9...

A012848

tanh(sec(x)*arctanh(x))=x+3/3!*x^3-15/5!*x^5-1869/7!*x^7-88959/9!*x^9...

Terms

    a(0) =1a(1) =3a(2) =-15a(3) =-1869a(4) =-88959a(5) =202499a(6) =974640433a(7) =190241481587

External references