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 A222138 #7 Jul 23 2025 02:24:38 %S A222138 4,52,676,8788,114244,1485172,19307236,250994068,3262922884, %T A222138 42417997492,551433967396,7168641576148,93192340489924, %U A222138 1211500426369012,15749505542797156,204743572056363028,2661666436732719364 %N A222138 Number of nX2 0..4 arrays with no entry increasing mod 5 by 4 rightwards or downwards, starting with upper left zero. %C A222138 Column 2 of A222144 %H A222138 R. H. Hardin, <a href="/A222138/b222138.txt">Table of n, a(n) for n = 1..210</a> %F A222138 Empirical: a(n) = 13*a(n-1) %e A222138 Some solutions for n=3 %e A222138 ..0..1....0..2....0..3....0..2....0..3....0..1....0..3....0..3....0..1....0..1 %e A222138 ..0..3....0..0....3..3....0..2....0..0....2..2....1..1....1..1....3..3....0..2 %e A222138 ..0..0....0..3....4..0....0..0....0..3....0..3....1..3....2..4....4..0....3..0 %K A222138 nonn %O A222138 1,1 %A A222138 _R. H. Hardin_ Feb 09 2013