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 A208046 #10 Mar 07 2018 02:31:12 %S A208046 5,32,244,1904,14976,118096,931968,7356288,58068800,458389760, %T A208046 3618506752,28564366592,225486229504,1779981604864,14051122574336, %U A208046 110919150841856,875592537571328,6911901929525248,54562352063938560,430713614487224320 %N A208046 Number of n X 4 0..3 arrays with new values 0..3 introduced in row major order and no element equal to any horizontal, vertical or antidiagonal neighbor (colorings ignoring permutations of colors). %C A208046 Column 4 of A208050. %H A208046 R. H. Hardin, <a href="/A208046/b208046.txt">Table of n, a(n) for n = 1..210</a> %F A208046 Empirical: a(n) = 12*a(n-1) - 40*a(n-2) + 68*a(n-3) - 64*a(n-4) for n>5. %F A208046 Empirical g.f.: x*(5 - 28*x + 60*x^2 - 84*x^3 + 32*x^4) / (1 - 12*x + 40*x^2 - 68*x^3 + 64*x^4). - _Colin Barker_, Mar 06 2018 %e A208046 Some solutions for n=4: %e A208046 0 1 2 1 0 1 2 0 0 1 0 1 0 1 2 3 0 1 2 3 %e A208046 2 3 0 2 2 0 1 2 2 3 2 3 2 3 0 1 2 3 0 1 %e A208046 1 2 1 3 1 3 0 1 0 1 0 1 0 1 3 0 1 2 3 2 %e A208046 3 0 2 0 2 1 2 3 2 3 2 0 2 0 2 1 3 1 0 1 %Y A208046 Cf. A208050. %K A208046 nonn %O A208046 1,1 %A A208046 _R. H. Hardin_, Feb 22 2012