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 A206230 #8 Jul 22 2025 19:20:07 %S A206230 15,256,4456,283728,10915392,1448239080,649065145152,203396423662488, %T A206230 222950396746461504,842104767130879914696,2305567526828592241306992, %U A206230 22136848571138455592306188104,737206270850592131066195723493312 %N A206230 Number of (n+1)X(n+1) 0..3 arrays with every 2X3 or 3X2 subblock having exactly two equal edges, and new values 0..3 introduced in row major order. %C A206230 Diagonal of A206238 %H A206230 R. H. Hardin, <a href="/A206230/b206230.txt">Table of n, a(n) for n = 1..16</a> %e A206230 Some solutions for n=4 %e A206230 ..0..1..0..0..1....0..1..0..0..1....0..0..1..2..0....0..1..2..1..0 %e A206230 ..2..0..0..1..0....0..0..2..0..0....0..3..2..2..0....1..2..2..1..1 %e A206230 ..0..0..1..0..0....1..0..0..3..0....3..2..2..0..1....2..2..0..2..2 %e A206230 ..2..2..0..0..1....2..3..0..0..1....2..2..3..1..1....0..0..2..2..3 %e A206230 ..3..2..0..2..0....2..2..3..0..0....2..3..1..1..0....3..0..2..3..0 %K A206230 nonn %O A206230 1,1 %A A206230 _R. H. Hardin_ Feb 05 2012