OFFSET
0,3
FORMULA
a(2*n + 1) = 1 for n >= 0.
3 divides a(2*n) for n >= 1.
MAPLE
gf := (cosh(x*z)+cos(x*z))*z/(1-exp(-z)): ser := series(gf, z, 70):
seq(denom(subs(x=1, n!*coeff(ser, z, n))), n=0..62);
MATHEMATICA
m = 62;
gf = (Cosh[x*z] + Cos[x*z])*z/(1 - E^-z);
Denominator[CoefficientList[(gf/.x->1)+O[z]^(m+1), z]*Range[0, m]!] (* Jean-François Alcover, Jun 04 2019 *)
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Peter Luschny, Aug 19 2018
STATUS
approved