arctanh(arctanh(x)*tan(x))=2/2!*x^2+16/4!*x^4+560/6!*x^6+39296/8!*x^8...

A012726

arctanh(arctanh(x)*tan(x))=2/2!*x^2+16/4!*x^4+560/6!*x^6+39296/8!*x^8...

Terms

    a(0) =0a(1) =2a(2) =16a(3) =560a(4) =39296a(5) =4768768a(6) =881315840a(7) =230827284480

External references