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 A303041 #4 Apr 17 2018 13:24:25 %S A303041 4,6,14,28,56,150,360,828,1906,4628,10972,25850,60948,145152,343870, %T A303041 814072,1927632,4573086,10836712,25678860,60851842,144253956, %U A303041 341881772,810275098,1920403380,4551789280,10788216718,25569422984,60602792000 %N A303041 Number of 3Xn 0..1 arrays with every element equal to 0, 1, 3, 4 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303041 Row 3 of A303040. %H A303041 R. H. Hardin, <a href="/A303041/b303041.txt">Table of n, a(n) for n = 1..210</a> %F A303041 Empirical: a(n) = 2*a(n-1) +2*a(n-2) -2*a(n-3) +6*a(n-4) -16*a(n-5) -11*a(n-6) +14*a(n-7) -4*a(n-8) +16*a(n-9) +4*a(n-10) -8*a(n-11) for n>12 %e A303041 Some solutions for n=5 %e A303041 ..0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..1 %e A303041 ..1..1..0..0..0. .0..1..1..1..0. .0..1..0..1..0. .0..1..0..0..0 %e A303041 ..0..1..0..1..0. .0..1..0..1..0. .0..1..1..1..0. .0..1..1..1..0 %Y A303041 Cf. A303040. %K A303041 nonn %O A303041 1,1 %A A303041 _R. H. Hardin_, Apr 17 2018