tan(arctanh(x)*arctan(x))=2/2!*x^2+448/6!*x^6+2138112/10!*x^10...

A012730

tan(arctanh(x)*arctan(x))=2/2!*x^2+448/6!*x^6+2138112/10!*x^10...

Terms

    a(0) =2a(1) =448a(2) =2138112a(3) =53551718400

External references