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 A263121 #4 Oct 10 2015 07:06:15 %S A263121 168,1664,10356,56288,238104,1294448,6844676,35274768,166684808, %T A263121 837700064,4262833076,21682367296,106913755512,530662478800, %U A263121 2665248077636,13441453266928,67154044231144,333650046421056 %N A263121 Number of (n+3)X(3+3) 0..1 arrays with each row divisible by 15 and column not divisible by 15, read as a binary number with top and left being the most significant bits. %C A263121 Column 3 of A263124. %H A263121 R. H. Hardin, <a href="/A263121/b263121.txt">Table of n, a(n) for n = 1..210</a> %e A263121 Some solutions for n=4 %e A263121 ..1..0..1..1..0..1....0..0..1..1..1..1....1..1..1..1..0..0....1..1..1..1..0..0 %e A263121 ..1..0..1..1..0..1....0..0..0..0..0..0....0..0..0..0..0..0....0..0..1..1..1..1 %e A263121 ..1..1..1..1..0..0....0..0..1..1..1..1....0..0..1..1..1..1....1..0..1..1..0..1 %e A263121 ..0..0..1..1..1..1....0..1..1..1..1..0....1..1..1..1..0..0....0..0..1..1..1..1 %e A263121 ..1..0..1..1..0..1....0..0..1..1..1..1....1..1..1..1..0..0....1..1..1..1..0..0 %e A263121 ..0..0..0..0..0..0....1..0..1..1..0..1....0..1..1..1..1..0....0..1..1..1..1..0 %e A263121 ..0..1..1..1..1..0....1..0..1..1..0..1....1..1..1..1..0..0....0..0..1..1..1..1 %Y A263121 Cf. A263124. %K A263121 nonn %O A263121 1,1 %A A263121 _R. H. Hardin_, Oct 10 2015