OFFSET
0,6
FORMULA
G.f.: A(x) = (1/x) * Series_Reversion(x / (1 - x - x^2 - x^3)).
MATHEMATICA
nmax = 33; A[_] = 0; Do[A[x_] = 1 - Sum[(x A[x])^k, {k, 1, 3}] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
nmax = 34; CoefficientList[(1/x) InverseSeries[Series[x/(1 - x - x^2 - x^3), {x, 0, nmax}], x], x]
b[m_, r_, k_] := b[m, r, k] = If[m + r == 0, 1, Sum[b[m - j, r + j - 1, k], {j, 1, Min[1, m]}] - Sum[b[m + j - 1, r - j, k], {j, 1, Min[k, r]}]]; a[n_] := b[0, n, 3]; Table[a[n], {n, 0, 33}]
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Aug 30 2020
STATUS
approved