sech(arctan(arcsinh(x)))=1-1/2!*x^2+17/4!*x^4-769/6!*x^6+66401/8!*x^8...

A012221

sech(arctan(arcsinh(x)))=1-1/2!*x^2+17/4!*x^4-769/6!*x^6+66401/8!*x^8...

Terms

    a(0) =1a(1) =-1a(2) =17a(3) =-769a(4) =66401a(5) =-9313281a(6) =1927198833a(7) =-551835917697

External references