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 A301840 #4 Mar 27 2018 14:30:45 %S A301840 64,2778,72514,1986213,54948498,1518341751,41966406867,1159968653556, %T A301840 32062561937804,886245421510973,24496909108346419,677125561489883191, %U A301840 18716618615716379268,517351460289528901541,14300262505893118372023 %N A301840 Number of nX7 0..1 arrays with every element equal to 0, 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301840 Column 7 of A301841. %H A301840 R. H. Hardin, <a href="/A301840/b301840.txt">Table of n, a(n) for n = 1..210</a> %H A301840 R. H. Hardin, <a href="/A301840/a301840.txt">Empirical recurrence of order 53</a> %F A301840 Empirical recurrence of order 53 (see link above) %e A301840 Some solutions for n=5 %e A301840 ..0..0..1..0..0..1..0. .0..0..1..0..0..1..0. .0..0..1..0..0..1..1 %e A301840 ..0..0..1..0..1..1..0. .0..0..1..0..0..1..1. .0..0..1..0..0..0..1 %e A301840 ..0..0..1..0..0..1..0. .0..0..1..0..1..0..0. .0..0..1..1..1..1..0 %e A301840 ..0..1..0..0..1..1..0. .1..0..0..1..0..1..1. .1..1..0..0..0..1..1 %e A301840 ..0..1..1..0..1..0..1. .1..1..0..1..0..1..1. .0..1..1..0..0..0..0 %Y A301840 Cf. A301841. %K A301840 nonn %O A301840 1,1 %A A301840 _R. H. Hardin_, Mar 27 2018