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 A375858 #12 Sep 03 2024 23:03:35 %S A375858 1,1,1,1,4,1,1,11,11,1,1,26,56,26,1,1,57,212,212,57,1,1,120,701,1112, %T A375858 701,120,1,1,247,2179,4793,4793,2179,247,1,1,502,6600,19082,25000, %U A375858 19082,6600,502,1,1,1013,19808,74368,116852,116852,74368,19808,1013,1 %N A375858 Array T(n,m) read by antidiagonals: In an n X m grid draw straight walls between cells, starting at a border, such that the resulting figure is connected and has only one-cell wide paths; T(n,m) is the number of solutions. %C A375858 See A375770 and A375817 for additional explanation and illustration of solutions. %C A375858 This sequence counts a subset of the spanning trees enumerated in A116469. %H A375858 Andrew Howroyd, <a href="/A375858/b375858.txt">Table of n, a(n) for n = 1..1275</a> (first 50 antidiagonals) %F A375858 T(n,m) = T(m,n). %e A375858 Array begins: %e A375858 ================================================== %e A375858 n/m | 1 2 3 4 5 6 7 ... %e A375858 ----+--------------------------------------------- %e A375858 1 | 1 1 1 1 1 1 1 ... %e A375858 2 | 1 4 11 26 57 120 247 ... %e A375858 3 | 1 11 56 212 701 2179 6600 ... %e A375858 4 | 1 26 212 1112 4793 19082 74368 ... %e A375858 5 | 1 57 701 4793 25000 116852 535776 ... %e A375858 6 | 1 120 2179 19082 116852 607712 3048668 ... %e A375858 7 | 1 247 6600 74368 535776 3048668 15918280 ... %e A375858 ... %o A375858 (PARI) \\ A375858(n,m) defined in PARI link in A375770. %Y A375858 Main diagonal is A375817. %Y A375858 Cf. A116469, A375770, A375859, A375860, A375861. %K A375858 nonn,tabl %O A375858 1,5 %A A375858 _Andrew Howroyd_, Aug 31 2024