OFFSET
1,3
MATHEMATICA
nn = 16; f[x_] := Product[(1 + a[n] x^(2 n)/(2 n)!), {n, 1, nn}]; sol = SolveAlways[0 == Series[f[x] - Cosh[x], {x, 0, 2 nn}], x]; Table[a[n], {n, 1, nn}] /. sol // Flatten
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, May 07 2022
STATUS
approved