arctanh(arctan(x)*tan(x))=2/2!*x^2+400/6!*x^6-2688/8!*x^8...

A012452

arctanh(arctan(x)*tan(x))=2/2!*x^2+400/6!*x^6-2688/8!*x^8...

Terms

    a(0) =0a(1) =2a(2) =0a(3) =400a(4) =-2688a(5) =1873408a(6) =-60938240a(7) =49450805248

External references