OFFSET
1,8
COMMENTS
Series reversion of the g.f. gives the same sequence with three initial terms (1, 1, 1) dropped.
FORMULA
G.f. satisfies A((A(x) - x - x^2 - x^3)/x^3) = x.
MATHEMATICA
Nest[InverseSeries[#] x^3 + x^3 + x^2 + x &, x + O[x]^2, 10][[3]]
CROSSREFS
KEYWORD
sign
AUTHOR
Vladimir Reshetnikov, Aug 08 2019
STATUS
approved