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 A196953 #7 Jun 02 2025 04:38:42 %S A196953 4,20,87,492,2687,14509,78717,427700,2320738,12593583,68356288, %T A196953 370995901,2013496775,10928042781,59310677884,321900611044, %U A196953 1747074166413,9482023129916,51462457739671,279305865035645,1515896714830837 %N A196953 Number of nX4 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 2,1,3,4,0 for x=0,1,2,3,4. %C A196953 Every 0 is next to 0 2's, every 1 is next to 1 1's, every 2 is next to 2 3's, every 3 is next to 3 4's, every 4 is next to 4 0's %C A196953 Column 4 of A196957 %H A196953 R. H. Hardin, <a href="/A196953/b196953.txt">Table of n, a(n) for n = 1..210</a> %F A196953 Empirical: a(n) = 2*a(n-1) +10*a(n-2) +37*a(n-3) +54*a(n-4) -39*a(n-6) -10*a(n-7) -37*a(n-8) -49*a(n-9) -18*a(n-10) -9*a(n-11) -16*a(n-12) +6*a(n-13) -a(n-14) +a(n-15) for n>16 %e A196953 Some solutions for n=5 %e A196953 ..0..0..0..0....0..0..1..1....0..0..1..1....0..0..0..0....0..0..1..1 %e A196953 ..0..0..0..0....0..1..0..0....1..0..0..0....1..0..0..0....0..0..0..0 %e A196953 ..0..4..0..0....0..1..0..0....1..0..1..1....1..0..4..0....0..4..0..0 %e A196953 ..0..0..1..0....0..0..0..1....0..0..0..0....0..0..0..1....0..0..0..0 %e A196953 ..0..0..1..0....0..0..0..1....0..0..1..1....0..0..0..1....1..1..0..0 %K A196953 nonn %O A196953 1,1 %A A196953 _R. H. Hardin_ Oct 08 2011