A012450 arcsinh(arctan(x)*tan(x))=2/2!*x^2+40/6!*x^6-2688/8!*x^8+210208/10!*x^10...

2, 0, 40, -2688, 210208, -13038080, 2241915520, -589026013184, 146361182839296, -42690102749216768, 18963982821764573184, -10109322351828827471872, 5702647873782168851521536

Offset: 1

Author

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

Keywords

• sign

Formula

a(n) = (2n)! [ x^(2n) ] arcsinh(arctan(x)*tan(x)).