sech(tanh(x)*arctan(x))=1-12/4!*x^4+480/6!*x^6-18480/8!*x^8...

A012687

sech(tanh(x)*arctan(x))=1-12/4!*x^4+480/6!*x^6-18480/8!*x^8...

Terms

    a(0) =1a(1) =0a(2) =-12a(3) =480a(4) =-18480a(5) =176640a(6) =149396544a(7) =-38742692352

External references