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 A239334 #6 Jun 02 2025 09:26:04 %S A239334 5,31,172,926,5078,27861,152260,832207,4550810,24881731,136029644, %T A239334 743697760,4065948624,22229220072,121530709245,664428372582, %U A239334 3632538661095,19859679158791,108576093277449,593603153333233 %N A239334 Number of nX2 0..3 arrays with no element equal to one plus the sum of elements to its left or three plus the sum of elements above it, modulo 4. %C A239334 Column 2 of A239340 %H A239334 R. H. Hardin, <a href="/A239334/b239334.txt">Table of n, a(n) for n = 1..210</a> %F A239334 Empirical: a(n) = 9*a(n-1) -28*a(n-2) +74*a(n-3) -181*a(n-4) +236*a(n-5) -261*a(n-6) +234*a(n-7) +200*a(n-8) -279*a(n-9) +104*a(n-10) -268*a(n-11) -36*a(n-12) +156*a(n-13) +104*a(n-14) -32*a(n-15) -16*a(n-16) %e A239334 Some solutions for n=5 %e A239334 ..2..0....2..0....2..0....2..1....2..2....0..2....0..2....2..1....2..2....2..1 %e A239334 ..3..2....2..1....3..1....2..1....0..3....0..2....0..0....2..2....0..2....2..2 %e A239334 ..3..3....0..2....3..2....0..2....3..1....2..0....0..2....2..0....2..1....2..1 %e A239334 ..2..2....0..3....2..0....0..0....3..3....0..2....2..0....3..1....0..3....3..1 %e A239334 ..3..1....0..0....0..3....0..0....2..1....0..0....3..1....2..0....0..0....3..1 %K A239334 nonn %O A239334 1,1 %A A239334 _R. H. Hardin_, Mar 16 2014