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 A301994 #12 Jul 14 2022 02:31:33 %S A301994 1,2,5,15,48,155,499,1602,5137,16467,52784,169199,542375,1738618, %T A301994 5573261,17865479,57269040,183579891,588478091,1886407378,6047009817, %U A301994 19384109803,62137109808,199184819687,638500768991,2046758546378,6561026627701 %N A301994 Number of n X 3 0..1 arrays with every element equal to 1, 2 or 4 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301994 Column 3 of A301999. %H A301994 R. H. Hardin, <a href="/A301994/b301994.txt">Table of n, a(n) for n = 1..210</a> %F A301994 Empirical: a(n) = 5*a(n-1) - 7*a(n-2) + 4*a(n-3). %F A301994 Empirical: partial sums of A049219. - _Sean A. Irvine_, Jul 13 2022 %e A301994 Some solutions for n=5: %e A301994 0 0 0 0 0 1 0 0 1 0 0 1 0 0 1 0 0 0 0 0 1 %e A301994 1 1 0 1 1 0 1 1 1 0 1 1 1 1 1 1 1 0 1 1 1 %e A301994 1 0 0 0 0 0 1 0 0 0 0 1 1 1 1 0 0 0 1 0 0 %e A301994 1 1 0 0 1 1 1 1 0 0 1 0 1 0 0 0 1 0 1 1 1 %e A301994 1 0 0 1 0 0 1 0 0 1 0 0 0 1 1 1 0 0 0 0 0 %Y A301994 Cf. A301999, A049219. %K A301994 nonn %O A301994 1,2 %A A301994 _R. H. Hardin_, Mar 30 2018