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 A303526 #4 Apr 25 2018 12:41:48 %S A303526 4,6,18,37,80,286,916,2532,7477,24285,76820,235117,731307,2316410, %T A303526 7294592,22810317,71569571,225378484,708826544,2225946457,6995090976, %U A303526 21998860077,69164809009,217385283885,683342646350,2148402980261 %N A303526 Number of 3Xn 0..1 arrays with every element equal to 0, 1, 3, 4, 5 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303526 Row 3 of A303525. %H A303526 R. H. Hardin, <a href="/A303526/b303526.txt">Table of n, a(n) for n = 1..210</a> %F A303526 Empirical: a(n) = 2*a(n-1) +3*a(n-2) +a(n-3) +30*a(n-4) -53*a(n-5) -102*a(n-6) +11*a(n-7) -227*a(n-8) +351*a(n-9) +784*a(n-10) -242*a(n-11) +351*a(n-12) -361*a(n-13) -1069*a(n-14) +577*a(n-15) +8*a(n-16) +28*a(n-17) +22*a(n-18) -11*a(n-19) -a(n-20) for n>21 %e A303526 Some solutions for n=5 %e A303526 ..0..0..0..1..0. .0..1..0..0..0. .0..0..1..0..1. .0..1..1..0..1 %e A303526 ..0..1..1..1..0. .0..1..1..1..0. .1..1..1..0..1. .1..0..1..0..1 %e A303526 ..0..1..0..1..0. .0..0..0..1..0. .1..0..0..0..1. .1..0..1..0..1 %Y A303526 Cf. A303525. %K A303526 nonn %O A303526 1,1 %A A303526 _R. H. Hardin_, Apr 25 2018