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 A204072 #7 Jul 22 2025 17:45:05 %S A204072 938,25277,706454,19934369,563880962,15960507749,451830740558, %T A204072 12791537916233,362138172985082,10252434870775373,290255213590923014, %U A204072 8217375177569472881,232640981675680448882,6586267002045127095221 %N A204072 Number of (n+1)X5 0..2 arrays with every 2X2 subblock having equal diagonal elements or equal antidiagonal elements, and new values 0..2 introduced in row major order. %C A204072 Column 4 of A204076 %H A204072 R. H. Hardin, <a href="/A204072/b204072.txt">Table of n, a(n) for n = 1..210</a> %F A204072 Empirical: a(n) = 32*a(n-1) -55*a(n-2) -1588*a(n-3) +5428*a(n-4) -2664*a(n-5) -3936*a(n-6) +3040*a(n-7) -256*a(n-8) %e A204072 Some solutions for n=4 %e A204072 ..0..0..0..1..1....0..0..0..1..2....0..1..0..2..1....0..1..1..1..2 %e A204072 ..0..2..0..0..1....2..0..0..0..1....2..0..1..0..2....1..2..1..2..0 %e A204072 ..0..0..2..0..0....1..2..0..2..0....1..2..0..0..0....1..1..2..2..2 %e A204072 ..1..0..0..0..1....2..2..2..0..2....0..1..2..0..0....1..2..2..1..2 %e A204072 ..0..0..0..2..0....1..2..1..2..0....0..0..1..2..0....0..1..2..2..1 %K A204072 nonn %O A204072 1,1 %A A204072 _R. H. Hardin_ Jan 10 2012