sech(arcsin(tan(x)))=1-1/2!*x^2-7/4!*x^4-121/6!*x^6-5167/8!*x^8...

A012086

sech(arcsin(tan(x)))=1-1/2!*x^2-7/4!*x^4-121/6!*x^6-5167/8!*x^8...

Terms

    a(0) =1a(1) =-1a(2) =-7a(3) =-121a(4) =-5167a(5) =-487441a(6) =-78804727a(7) =-18558463561

External references