A009371 Expansion of log(1+tan(x))*exp(x).

0, 1, 1, 4, 0, 45, -155, 1748, -13496, 151169, -1682191, 22018412, -307464872, 4746159613, -78744546907, 1410956472396, -27026759291728, 552443153007777, -11988735452427903, 275451486233018100, -6677966707663119664

Offset: 0

Author

R. H. Hardin

Keywords

• sign
• easy

Programs

Mathematica

Log[ 1+Tan[ x ] ]*Exp[ x ]
CoefficientList[Series[E^x*Log[1 + Tan[x]], {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 23 2015 *)

Formula

a(n) ~ (n-1)! * (-1)^(n+1) * exp(-Pi/4) * (4/Pi)^n. - Vaclav Kotesovec, Jan 23 2015

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997