OFFSET
0,4
REFERENCES
V. Mangulis, Handbook of Series, Academic Press, 1965, p. 76.
FORMULA
log(z^2/(cosh(z)-cos(z))) = Sum_{ n >= 1 } (-1)^n*B_{2n}*(2z^2)^(2n)/((4n)!2n).
a(n) = numerator((-1)^n * zeta(4*n)/(zeta(2*n)*Pi^(2*n))). - Enrique Pérez Herrero, Jun 20 2012
EXAMPLE
log(z^2/(cosh(z)-cos(z))) = -(1/360)*z^4+(1/302400)*z^8-(691/122594472000)*z^12+(3617/333456963840000)*z^16+...
PROG
(PARI) my(N=90, z='z+O('z^N), v=apply(numerator, Vec(log(z^2/(cosh(z)-cos(z))), -N))); vector(#v\4, k, v[4*k-2]) \\ Michel Marcus, Feb 03 2025
CROSSREFS
KEYWORD
sign,frac
AUTHOR
N. J. A. Sloane, Oct 31 2009
EXTENSIONS
Definition clarified by Michel Marcus, Feb 03 2025
STATUS
approved