A009373 Expansion of log(1+tan(x))/cosh(x).

0, 1, -1, 1, -8, 65, -361, 2497, -23848, 256385, -2904601, 36778113, -520366208, 8014148545, -132884846641, 2373343120449, -45463597872688, 928532354406145, -20134914035881681, 462226423647925505, -11199802803793004888

Offset

0,5

Links

Table of n, a(n) for n=0..20.

Formula

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

Mathematica

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

Crossrefs

Sequence in context: A316205 A305772 A317121 * A305589 A317007 A293802

Adjacent sequences: A009370 A009371 A009372 * A009374 A009375 A009376

Keyword

sign,easy

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved