arctan(tanh(x)*tan(x))=2/2!*x^2-128/6!*x^6+253952/10!*x^10...

A012670

arctan(tanh(x)*tan(x))=2/2!*x^2-128/6!*x^6+253952/10!*x^10...

Terms

    a(0) =2a(1) =-128a(2) =253952a(3) =-2863136768

External references