sech(tan(tanh(x)))=1-1/2!*x^2+5/4!*x^4-13/6!*x^6-1751/8!*x^8...

A012173

sech(tan(tanh(x)))=1-1/2!*x^2+5/4!*x^4-13/6!*x^6-1751/8!*x^8...

Terms

    a(0) =1a(1) =-1a(2) =5a(3) =-13a(4) =-1751a(5) =132871a(6) =-6935699a(7) =5067579a(8) =89435340497

External references