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 A229412 #6 Jul 23 2025 05:43:46 %S A229412 4,15,15,57,163,57,216,1756,1756,216,819,18712,53538,18712,819,3105, %T A229412 199595,1629298,1629298,199595,3105,11772,2127718,49788258,142475606, %U A229412 49788258,2127718,11772,44631,22684613,1519840402,12462062342 %N A229412 T(n,k)=Number of nXk 0..3 arrays avoiding 11 horizontally, 22 vertically, 33 antidiagonally and 00 diagonally. %C A229412 Table starts %C A229412 .....4........15............57..............216..................819 %C A229412 ....15.......163..........1756............18712...............199595 %C A229412 ....57......1756.........53538..........1629298.............49788258 %C A229412 ...216.....18712.......1629298........142475606..........12462062342 %C A229412 ...819....199595......49788258......12462062342........3113479414050 %C A229412 ..3105...2127718....1519840402....1088122273732......777638567093963 %C A229412 .11772..22684613...46408035676...95053083585891...194334416016079648 %C A229412 .44631.241841143.1416912709750.8301763765531574.48554820719187209670 %H A229412 R. H. Hardin, <a href="/A229412/b229412.txt">Table of n, a(n) for n = 1..220</a> %F A229412 Empirical for column k: %F A229412 k=1: a(n) = 3*a(n-1) +3*a(n-2) %F A229412 k=2: a(n) = 10*a(n-1) +13*a(n-2) -67*a(n-3) +38*a(n-4) -2*a(n-5) %F A229412 k=3: [order 13] %F A229412 k=4: [order 40] %e A229412 Some solutions for n=3 k=4 %e A229412 ..0..0..0..3....0..2..0..2....0..0..3..0....0..0..2..2....0..0..3..0 %e A229412 ..3..2..2..2....0..1..0..1....0..2..1..0....3..3..1..3....2..2..2..1 %e A229412 ..3..0..1..3....0..2..3..3....2..3..0..3....1..3..2..0....0..0..1..3 %Y A229412 Column 1 is A125145 %K A229412 nonn,tabl %O A229412 1,1 %A A229412 _R. H. Hardin_ Sep 22 2013