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 A267902 #6 Aug 12 2016 06:54:16 %S A267902 0,2,3,11,29,93,268,842,2547,7946,24539,76721,239462,751569,2360679, %T A267902 7437243,23461543,74155431,234687456,743792675,2359972537,7496293462, %U A267902 23834595755,75852059135,241594260984,770090455545,2456436981617 %N A267902 Number of 2Xn arrays containing n copies of 0..2-1 with every element equal to at least one horizontal or vertical neighbor and the top left element equal to 0. %C A267902 Row 2 of A267901. %H A267902 R. H. Hardin, <a href="/A267902/b267902.txt">Table of n, a(n) for n = 1..210</a> %e A267902 Some solutions for n=4 %e A267902 ..0..1..0..1....0..0..1..1....0..1..1..1....0..0..1..0....0..0..0..1 %e A267902 ..0..1..0..1....1..1..0..0....0..0..0..1....1..1..1..0....1..1..0..1 %Y A267902 Cf. A267901. %K A267902 nonn %O A267902 1,2 %A A267902 _R. H. Hardin_, Jan 22 2016