OFFSET
0,4
MAPLE
E2poly := (n, x) -> add(A340556(n, k)*x^k, k = 0..n):
seq(2^n*E2poly(n, -1/2), n = 0..21);
# By series reversion:
serrev := proc(gf, len) series(gf, y, len);
gfun:-seriestoseries(%, 'revogf'); gfun:-seriestolist(%);
gfun:-listtolist(%, 'Laplace'); subsop(1 = NULL, %) end:
gf := (6*y + exp(3*y) - 1)/9: serrev(gf, 23);
MATHEMATICA
R := 22; f[y_] := (6y + Exp[3y] - 1)/9;
S := InverseSeries[Series[f[y], {y, 0, R}], x];
Drop[CoefficientList[S, x] Table[n!, {n, 0, R}], 1]
CROSSREFS
KEYWORD
sign
AUTHOR
Peter Luschny, Feb 13 2021
STATUS
approved