sech(arctan(arctan(x)))=1-1/2!*x^2+21/4!*x^4-1149/6!*x^6+119305/8!*x^8...
A012211
sech(arctan(arctan(x)))=1-1/2!*x^2+21/4!*x^4-1149/6!*x^6+119305/8!*x^8...
Terms
- a(0) =1a(1) =-1a(2) =21a(3) =-1149a(4) =119305a(5) =-20082841a(6) =4984310493
External references
- oeis: A012211