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 A197532 #7 Jun 02 2025 04:58:40 %S A197532 4,16,56,216,868,3500,14085,56842,229706,928664,3755722,15191220, %T A197532 61451640,248596817,1005703793,4068662528,16460279703,66592450774, %U A197532 269410213656,1089943115100,4409547400430,17839571907124,72173035560719 %N A197532 Number of nX3 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 2,0,1,0,0 for x=0,1,2,3,4. %C A197532 Every 0 is next to 0 2's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 0's, every 4 is next to 4 0's %C A197532 Column 3 of A197537 %H A197532 R. H. Hardin, <a href="/A197532/b197532.txt">Table of n, a(n) for n = 1..200</a> %F A197532 Empirical: a(n) = 4*a(n-1) +5*a(n-2) -15*a(n-3) -21*a(n-4) +3*a(n-5) +28*a(n-6) +32*a(n-7) -5*a(n-8) -57*a(n-9) +10*a(n-10) +90*a(n-11) +44*a(n-12) -14*a(n-13) -101*a(n-14) -56*a(n-15) +46*a(n-16) +14*a(n-17) +11*a(n-18) -20*a(n-19) +9*a(n-20) +10*a(n-21) -9*a(n-22) -a(n-25) %e A197532 Some solutions for n=4 %e A197532 ..0..0..1....1..0..0....0..0..0....0..3..0....1..1..1....1..0..0....0..0..0 %e A197532 ..1..1..1....2..3..0....3..0..3....0..0..3....0..0..0....1..0..3....0..0..3 %e A197532 ..1..1..0....1..0..0....0..3..0....3..0..0....3..0..3....2..3..0....0..0..0 %e A197532 ..0..1..1....1..0..0....1..2..1....0..3..0....0..0..0....1..0..0....1..1..1 %K A197532 nonn %O A197532 1,1 %A A197532 _R. H. Hardin_ Oct 16 2011