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 A253294 #6 Apr 22 2021 14:18:08 %S A253294 81,558,558,3844,3600,3844,26784,23546,23546,26784,186624,167832, %T A253294 140536,167832,186624,1296000,1184928,1029888,1029888,1184928,1296000, %U A253294 9000000,8243488,7431136,8153960,7431136,8243488,9000000,62568000,57474376 %N A253294 T(n,k) = Number of (n+1) X (k+1) 0..2 arrays with every 2 X 2 subblock sum differing from its neighbors horizontally, vertically, diagonally and antidiagonally. %C A253294 Table starts %C A253294 .........81.........558.........3844........26784.......186624......1296000 %C A253294 ........558........3600........23546.......167832......1184928......8243488 %C A253294 .......3844.......23546.......140536......1029888......7431136.....52784020 %C A253294 ......26784......167832......1029888......8153960.....61286116....465921688 %C A253294 .....186624.....1184928......7431136.....61286116....486417836...4028778100 %C A253294 ....1296000.....8243488.....52784020....465921688...4028778100..36312321352 %C A253294 ....9000000....57474376....376392916...3524494796..32585471254.317292582684 %C A253294 ...62568000...402165016...2705942488..26879615668.268974784168 %C A253294 ..434972736..2811886280..19441124904.204459584768 %C A253294 .3022785216.19648735840.139538118106 %H A253294 R. H. Hardin, <a href="/A253294/b253294.txt">Table of n, a(n) for n = 1..84</a> %F A253294 Empirical for column k: %F A253294 k=1: [linear recurrence of order 9]; %F A253294 k=2: [order 40]. %e A253294 Some solutions for n=3, k=4 %e A253294 ..0..0..0..0..2....0..0..0..1..0....0..0..1..2..2....0..0..0..1..2 %e A253294 ..2..0..0..2..1....0..2..2..2..0....0..2..1..2..1....0..0..1..2..2 %e A253294 ..1..0..1..1..2....0..1..2..2..0....2..2..0..0..1....2..0..2..0..2 %e A253294 ..2..1..0..1..1....0..1..1..1..0....1..2..0..2..2....1..2..0..0..1 %Y A253294 Column 1 is A185771. %K A253294 nonn,tabl %O A253294 1,1 %A A253294 _R. H. Hardin_, Dec 29 2014