A012465 cosh(arctan(x)*arctan(x))=1+12/4!*x^4-480/6!*x^6+31248/8!*x^8...

1, 0, 12, -480, 31248, -3160320, 462297792, -92467554816, 24237361774848, -8058187934539776, 3312017870282345472, -1648428171351870627840, 976764310209146448384000, -679332936418413117235200000

Offset: 0

Author

Patrick Demichel (patrick.demichel(AT)hp.com)

Keywords

• sign

Programs

Mathematica

nn = 20; Table[(CoefficientList[Series[Cosh[ArcTan[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Feb 08 2015 *)