This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A288027 #22 Feb 16 2025 08:33:47 %S A288027 0,2,38,1834,419710,356269056,1163645044100,15000387107144576, %T A288027 749707067231291403016 %N A288027 Number of minimal edge covers in the grid graph P_n X P_n. %C A288027 A minimal edge cover is an edge cover such that the removal of any edge in the cover destroys the covering property. Equivalently, these are the edge covers whose connected components are stars. %H A288027 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GridGraph.html">Grid Graph</a> %H A288027 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MinimalEdgeCover.html">Minimal Edge Cover</a> %e A288027 In the 3 X 3 grid, the minimal edge covers up to rotation and reflection are: %e A288027 .__.__. .__.__. .__.__. .__.__. .__.__. .__. . %e A288027 .__.__. . . . .__. . . .__. . | . . | | %e A288027 .__.__. | | | .__. | |__. | | .__| | .__. %e A288027 The first two of these need to be counted 2 and 4 times and the rest which have no symmetry 8 times so a(3) = 38. %Y A288027 Main diagonal of A288025. %Y A288027 Cf. A286913. %K A288027 nonn,more %O A288027 1,2 %A A288027 _Andrew Howroyd_, Jun 04 2017 %E A288027 a(1) corrected by _Andrew Howroyd_, Jan 29 2023