arctan(arctanh(x)*arctan(x))=2/2!*x^2-32/6!*x^6+283392/10!*x^10...

A012731

arctan(arctanh(x)*arctan(x))=2/2!*x^2-32/6!*x^6+283392/10!*x^10...

Terms

    a(0) =2a(1) =-32a(2) =283392a(3) =1121740800

External references