A009375 Expansion of e.g.f.: 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

With[{nn=20}, CoefficientList[Series[Log[1+Tan[x]Cosh[x]], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jan 10 2025 *)
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

Definition clarified and first Mathematica program replaced by Harvey P. Dale, Jan 10 2025

Status

approved