cosh(arctan(arctan(x)))=1+1/2!*x^2-15/4!*x^4+609/6!*x^6-48031/8!*x^8...

A012210

cosh(arctan(arctan(x)))=1+1/2!*x^2-15/4!*x^4+609/6!*x^6-48031/8!*x^8...

Terms

    a(0) =1a(1) =1a(2) =-15a(3) =609a(4) =-48031a(5) =6247681a(6) =-1214813487a(7) =330587407201

External references