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 A301965 #4 Mar 29 2018 13:02:49 %S A301965 4,13,16,25,41,74,132,239,437,800,1468,2697,4957,9114,16760,30823, %T A301965 56689,104264,191768,352713,648737,1193210,2194652,4036591,7424445, %U A301965 13655680,25116708,46196825,84969205,156282730,287448752,528700679,972432153 %N A301965 Number of 3Xn 0..1 arrays with every element equal to 0, 1 or 4 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301965 Row 3 of A301964. %H A301965 R. H. Hardin, <a href="/A301965/b301965.txt">Table of n, a(n) for n = 1..210</a> %F A301965 Empirical: a(n) = 2*a(n-1) -a(n-4) for n>6 %e A301965 Some solutions for n=5 %e A301965 ..0..0..1..1..0. .0..1..0..1..0. .0..0..1..1..0. .0..1..0..0..1 %e A301965 ..1..0..0..1..0. .0..0..0..1..1. .1..0..0..1..1. .0..1..1..0..1 %e A301965 ..1..1..0..1..1. .0..1..0..0..1. .1..1..0..0..1. .0..0..1..0..1 %Y A301965 Cf. A301964. %K A301965 nonn %O A301965 1,1 %A A301965 _R. H. Hardin_, Mar 29 2018