A009367 Expansion of e.g.f.: log(1+tan(tanh(x))).

0, 1, -1, 2, -6, 16, -72, 496, -3248, 24064, -208384, 1908224, -19624704, 227958784, -2800573440, 36620830720, -519452284928, 7865201852416, -126035093291008, 2142236553248768, -38449509963399168, 725477781101608960

Offset

0,4

Links

Table of n, a(n) for n=0..21.

Formula

a(n) ~ (n-1)! * (-1)^(n+1) * 2^n / (log((4+Pi)/(4-Pi)))^n. - Vaclav Kotesovec, Jan 23 2015

Mathematica

With[{nn=30}, CoefficientList[Series[Log[1+Tan[Tanh[x]]], {x, 0, nn}], x]Range[0, nn]!] (* Harvey P. Dale, Sep 14 2012 *)

Crossrefs

Sequence in context: A009186 A009328 A009346 * A114249 A147910 A147902

Adjacent sequences: A009364 A009365 A009366 * A009368 A009369 A009370

Keyword

sign,easy

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Definition clarified by Harvey P. Dale, Sep 14 2012

Status

approved