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 A208347 #7 Jun 02 2025 07:43:52 %S A208347 2,15,100,868,7780,69988,629860,5668708,51018340,459165028,4132485220, %T A208347 37192366948,334731302500,3012581722468,27113235502180, %U A208347 244019119519588,2196172075676260,19765548681086308,177889938129776740 %N A208347 Number of nX2 0..3 arrays with new values 0..3 introduced in row major order and no element equal to any knight-move neighbor (colorings ignoring permutations of colors). %C A208347 Column 2 of A208353 %H A208347 R. H. Hardin, <a href="/A208347/b208347.txt">Table of n, a(n) for n = 1..210</a> %F A208347 Empirical: a(n) = 10*a(n-1) -9*a(n-2) for n>4 %e A208347 Some solutions for n=4 %e A208347 ..0..0....0..1....0..0....0..0....0..0....0..0....0..1....0..0....0..0....0..0 %e A208347 ..0..0....1..0....0..0....0..0....1..0....1..1....1..2....0..0....0..0....1..0 %e A208347 ..1..1....0..1....1..2....1..1....1..1....1..1....0..1....1..1....1..2....1..1 %e A208347 ..2..2....1..2....3..2....1..1....1..0....0..0....0..0....1..2....1..3....1..2 %K A208347 nonn %O A208347 1,1 %A A208347 _R. H. Hardin_ Feb 25 2012