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A009044 Expansion of cos(sin(x))/cosh(x), even terms only. 1
1, -2, 16, -248, 6336, -244480, 13409408, -999327488, 97590304768, -12120423043072, 1867576863899648, -349745166753398784, 78248003933970006016, -20613585750577859067904, 6315933020629432945606656 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..242

FORMULA

a(n) ~ (2*n)! * (-1)^n * cosh(sinh(Pi/2)) * 4^(n+1) / Pi^(2*n+1). - Vaclav Kotesovec, Jan 22 2015

MATHEMATICA

nn = 20; Table[(CoefficientList[Series[Cos[Sin[x]]*Sech[x], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Jan 22 2015 *)

PROG

(PARI) x='x+O('x^50); v=Vec(serlaplace(cos(sin(x))/cosh(x))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 23 2018

CROSSREFS

Sequence in context: A012457 A138764 A009833 * A019318 A090727 A108242

Adjacent sequences:  A009041 A009042 A009043 * A009045 A009046 A009047

KEYWORD

sign

AUTHOR

R. H. Hardin

EXTENSIONS

Extended with signs by Olivier Gérard, Mar 15 1997

STATUS

approved

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Last modified June 5 23:10 EDT 2020. Contains 334858 sequences. (Running on oeis4.)