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 A240625 #7 Jul 23 2025 11:02:42 %S A240625 2,10,109,1332,16624,208015,2604059,32601488,408158709,5110007540, %T A240625 63975568178,800952543871,10027655890879,125542872147582, %U A240625 1571754448134085,19677835970041564,246359874423207164 %N A240625 Number of nX2 0..3 arrays with no element equal to exactly two horizontal and vertical neighbors, with new values 0..3 introduced in row major order. %C A240625 Column 2 of A240629 %H A240625 R. H. Hardin, <a href="/A240625/b240625.txt">Table of n, a(n) for n = 1..210</a> %F A240625 Empirical: a(n) = 14*a(n-1) -14*a(n-2) -60*a(n-3) +29*a(n-4) +150*a(n-5) -47*a(n-6) -124*a(n-7) -4*a(n-8) +84*a(n-9) -27*a(n-10) for n>11 %e A240625 Some solutions for n=4 %e A240625 ..0..1....0..1....0..1....0..0....0..1....0..1....0..1....0..1....0..0....0..1 %e A240625 ..0..0....1..0....2..2....1..2....0..2....2..3....2..2....2..0....1..2....0..2 %e A240625 ..0..2....2..1....0..1....3..2....1..0....3..1....1..1....1..3....2..1....3..0 %e A240625 ..3..3....2..3....0..1....3..1....3..3....0..0....2..0....1..2....3..3....2..3 %K A240625 nonn %O A240625 1,1 %A A240625 _R. H. Hardin_, Apr 09 2014