A012670 arctan(tanh(x)*tan(x))=2/2!*x^2-128/6!*x^6+253952/10!*x^10...

2, -128, 253952, -2863136768, 107451055603712, -10140668012798148608, 2022780765718183801782272, -757569427466144902069404827648

Offset: 0

Author

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

Keywords

• sign

Formula

(-1)^n * 2^(6n+1) * A090681(n).