sech(tan(tan(x))) = 1-1/2!*x^2-11/4!*x^4-253/6!*x^6-9015/8!*x^8 ... .

A012154

sech(tan(tan(x))) = 1-1/2!*x^2-11/4!*x^4-253/6!*x^6-9015/8!*x^8 ... .

Terms

    a(0) =1a(1) =-1a(2) =-11a(3) =-253a(4) =-9015a(5) =-362009a(6) =2294909a(7) =7143505067

External references