sech(tanh(x)*cos(x))=1-1/2!*x^2+25/4!*x^4-1057/6!*x^6+81905/8!*x^8...

A012692

sech(tanh(x)*cos(x))=1-1/2!*x^2+25/4!*x^4-1057/6!*x^6+81905/8!*x^8...

Terms

    a(0) =1a(1) =-1a(2) =25a(3) =-1057a(4) =81905a(5) =-10280289a(6) =1887120585a(7) =-476966767617

External references