sech(cos(x)*arctan(x))=1-1/2!*x^2+25/4!*x^4-1105/6!*x^6+91313/8!*x^8...

A012508

sech(cos(x)*arctan(x))=1-1/2!*x^2+25/4!*x^4-1105/6!*x^6+91313/8!*x^8...

Terms

    a(0) =1a(1) =-1a(2) =25a(3) =-1105a(4) =91313a(5) =-12232385a(6) =2400320393a(7) =-649247356433

External references