OFFSET
1,2
COMMENTS
Reversion of g.f. (with constant term omitted) for A000698.
LINKS
N. J. A. Sloane, Transforms
Eric Weisstein's World of Mathematics, Series Reversion
FORMULA
G.f. A(x) satisfies: A(x)/(1 - 2*A(x)/(1 - 3*A(x)/(1 - 4*A(x)/(1 - 5*A(x)/(1 - ...))))) = x.
a(n) ~ -2^(n + 1/2) * n^n / exp(n+1). - Vaclav Kotesovec, May 07 2024
MATHEMATICA
Rest[CoefficientList[InverseSeries[Series[x/(1 + ContinuedFractionK[-i x, 1, {i, 2, 20}]), {x, 0, 20}], x], x]]
Rest[CoefficientList[InverseSeries[Series[1 - 1/(1 + Sum[(2 i - 1)!! x^i, {i, 1, 20}]), {x, 0, 20}], x], x]]
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Aug 23 2017
STATUS
approved