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 A240518 #6 Jul 23 2025 11:02:21 %S A240518 21,86,515,3765,28942,231665,1906245,16000486,135790448,1158315893, %T A240518 9946076742,85823282205,743139183617,6451236349918,56119492560507, %U A240518 488978060398481,4265874977466648,37250999894755072,325525391487428809 %N A240518 Number of nX7 0..1 arrays with no element equal to exactly two horizontal and vertical neighbors, with new values 0..1 introduced in row major order. %C A240518 Column 7 of A240519 %H A240518 R. H. Hardin, <a href="/A240518/b240518.txt">Table of n, a(n) for n = 1..169</a> %e A240518 Some solutions for n=4 %e A240518 ..0..1..0..1..0..1..0....0..1..1..1..0..1..0....0..1..0..1..0..1..0 %e A240518 ..0..1..0..1..0..1..0....1..0..1..0..1..1..1....1..0..1..1..0..0..1 %e A240518 ..1..0..1..0..1..0..1....0..1..0..1..0..1..0....0..0..0..1..0..1..1 %e A240518 ..0..1..1..1..0..1..0....1..1..1..0..1..0..1....1..0..1..0..1..0..1 %K A240518 nonn %O A240518 1,1 %A A240518 _R. H. Hardin_, Apr 06 2014