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%I #11 Feb 14 2023 16:32:25
%S 1,0,2,1,8,12,45,98,292,725,2004,5210,14051,37126,99336,263991,704622,
%T 1876566,5005327,13341292,35579622,94866875,252998042,674677856,
%U 1799331865,4798687520,12798199466,34133165825,91035612400,242799614636,647572193925,1727149489058
%N Number of solutions to a 4 X n Ring-Ring puzzle on an empty grid.
%H George Spahn, <a href="https://arxiv.org/abs/2202.06234">Enumerating solutions to grid based puzzles with a fixed number of rows</a>, arXiv:2202.06234 [math.CO], Feb 2022.
%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (3,3,-10,-3,5,1).
%F G.f.: -(2*x^2 + x - 1)*(x^2 + 2*x - 1)/(x^6 + 5*x^5 - 3*x^4 - 10*x^3 + 3*x^2 + 3*x - 1).
%K nonn,easy
%O 0,3
%A _George Spahn_, Feb 13 2023