A009375 Expansion of log(1+tan(x)*cosh(x)).

0, 1, -1, 7, -26, 165, -1216, 10827, -111376, 1316585, -17441536, 257028847, -4164440576, 73616009805, -1409649350656, 29070305745267, -642306123237376, 15137914082015825, -379068323095576576, 10050622525103392087

Offset

0,4

Links

Table of n, a(n) for n=0..19.

Formula

a(n) ~ (n-1)! * (-1)^(n+1) / r^n, where r = 0.678886646361824692174613333109767742222867349... is the root of the equation cosh(r)*tan(r) = 1. - Vaclav Kotesovec, Jan 24 2015

Mathematica

Log[ 1+Tan[ x ]*Cosh[ x ]]
CoefficientList[Series[Log[1 + Cosh[x]*Tan[x]], {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 24 2015 *)

Crossrefs

Sequence in context: A319425 A026683 A197053 * A009380 A183329 A342930

Adjacent sequences: A009372 A009373 A009374 * A009376 A009377 A009378

Keyword

sign,easy

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved