**Expansion of (1-2x-sqrt(1-4x))/(1+2x+sqrt(1-4x))/x^2.**

*1, 2, 6, 18, 57, 186, 622, 2120, 7338, 25724, 91144, 325878, 1174281, 4260282*

*1 seqfan posts*

Index of A-numbers in seqfan: by ascending order by month by frequency by keyword

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