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 A297583 #8 Mar 01 2019 06:20:43 %S A297583 1,5,11,17,39,93,183,373,823,1741,3599,7637,16247,34125,71871,152133, %T A297583 321127,676861,1429135,3017909,6367607,13437869,28367775,59874021, %U A297583 126360711,266707549,562939183,1188130069,2507681687,5292853517 %N A297583 Number of 2 X n 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 1 or 4 neighboring 1s. %H A297583 R. H. Hardin, <a href="/A297583/b297583.txt">Table of n, a(n) for n = 1..210</a> %F A297583 Empirical: a(n) = a(n-1) + 4*a(n-3) + 2*a(n-4). %F A297583 Empirical g.f.: x*(1 + 4*x + 6*x^2 + 2*x^3) / (1 - x - 4*x^3 - 2*x^4). - _Colin Barker_, Mar 01 2019 %e A297583 Some solutions for n=7: %e A297583 ..0..0..0..0..0..0..0. .0..1..0..0..0..1..0. .1..1..1..0..0..0..0 %e A297583 ..0..1..1..0..0..1..1. .1..0..0..0..0..0..1. .1..0..1..0..0..1..1 %Y A297583 Row 2 of A297582. %K A297583 nonn %O A297583 1,2 %A A297583 _R. H. Hardin_, Jan 01 2018