A009422 Expansion of log(1+x)*log(1+tan(x)).

0, 0, 2, -6, 30, -160, 1084, -8316, 74456, -749184, 8474240, -106035424, 1459781056, -21914009728, 356711937152, -6258266154752, 117778607150592, -2366994133647360, 50601711980789760, -1146653711692951552

Offset: 0

Author

R. H. Hardin

Keywords

• sign
• easy

Programs

Mathematica

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

Formula

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

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997