cosh(sec(x)*arctanh(x))=1+1/2!*x^2+21/4!*x^4+765/6!*x^6+46473/8!*x^8...

A012850

cosh(sec(x)*arctanh(x))=1+1/2!*x^2+21/4!*x^4+765/6!*x^6+46473/8!*x^8...

Terms

    a(0) =1a(1) =1a(2) =21a(3) =765a(4) =46473a(5) =4371225a(6) =594635613a(7) =110691178325

External references