OFFSET
1,2
COMMENTS
Row sums give A319028.
LINKS
Colin Defant, Stack-sorting preimages of permutation classes, arXiv:1809.03123 [math.CO], 2018.
FORMULA
G.f.: G(x,y) + x^3*y*((d/dx)G(x,y))^2, where G(x,y) = (1 - 2x - sqrt((1-2x)^2 - 4x^2*y))/(2x*y) is the generating function of A091894.
EXAMPLE
Triangle begins:
1,
2,
4, 2,
8, 14,
16, 64, 8,
32, 240, 92,
64, 800, 624, 34,
128, 2464, 3248, 534,
...
MATHEMATICA
DeleteCases[Flatten[CoefficientList[Series[(1 - 2 x - Sqrt[(1 - 2 x)^2 - 4 x^2 y])/(2 x*y) + x^3*y (D[(1 - 2 x - Sqrt[(1 - 2 x)^2 - 4 x^2 y])/(2 x*y), x])^2, {x, 0, 10}], {x, y}]], 0]
CROSSREFS
KEYWORD
easy,nonn,tabf
AUTHOR
Colin Defant, Sep 10 2018
STATUS
approved