A009380 Expansion of log(1+tan(x)/cos(x)).

0, 1, -1, 7, -26, 185, -1336, 12367, -129296, 1558865, -21045376, 316097527, -5218370816, 94003171145, -1834192393216, 38543705698687, -867785366030336, 20840298552277025, -531767959826169856, 14366953364916735847

Offset

0,4

Links

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

Formula

a(n) ~ (n-1)! * (-1)^(n+1) / (arctan(sqrt((sqrt(5)-1)/2)))^n. - Vaclav Kotesovec, Jan 23 2015

Mathematica

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

Crossrefs

Sequence in context: A026683 A197053 A009375 * A183329 A342930 A166406

Adjacent sequences: A009377 A009378 A009379 * A009381 A009382 A009383

Keyword

sign,easy

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved