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 A359993 #13 Feb 16 2025 08:34:04 %S A359993 1,1,1,1,5,1,1,23,23,1,1,105,431,105,1,1,479,7857,7857,479,1,1,2185, %T A359993 142625,555195,142625,2185,1,1,9967,2587279,38757695,38757695,2587279, %U A359993 9967,1,1,45465,46929343,2698167665,10286937043,2698167665,46929343,45465,1 %N A359993 Array read by antidiagonals: T(m,n) is the number of connected spanning subgraphs in the grid graph P_m X P_n. %C A359993 Also T(m,n) except when m = n = 0 is the number of connected edge covers in the m X n grid graph. %H A359993 Andrew Howroyd, <a href="/A359993/b359993.txt">Table of n, a(n) for n = 1..465</a> %H A359993 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GridGraph.html">Grid Graph</a> %F A359993 T(m,n) = T(n,m). %e A359993 Table starts: %e A359993 ================================================================= %e A359993 m\n| 1 2 3 4 5 6 %e A359993 ---+------------------------------------------------------------- %e A359993 1 | 1 1 1 1 1 1 ... %e A359993 2 | 1 5 23 105 479 2185 ... %e A359993 3 | 1 23 431 7857 142625 2587279 ... %e A359993 4 | 1 105 7857 555195 38757695 2698167665 ... %e A359993 5 | 1 479 142625 38757695 10286937043 2711895924889 ... %e A359993 6 | 1 2185 2587279 2698167665 2711895924889 2692324030864335 ... %e A359993 ... %Y A359993 Rows 1..4 are A000012, A107839(n-1), A158453, A359991. %Y A359993 Main diagonal is A359992. %Y A359993 Cf. A116469 (spanning trees), A287151 (connected induced subgraphs), A286912 (edge covers), A359990 (edge cuts), A360194 (spanning forests). %K A359993 nonn,tabl %O A359993 1,5 %A A359993 _Andrew Howroyd_, Jan 28 2023