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 A208040 #7 Apr 17 2022 17:47:32 %S A208040 9,81,279,961,4743,23409,100215,429025,1942075,8791225,38933415, %T A208040 172423161,770225067,3440643649,15317395695,68191488225,303989603715, %U A208040 1355149763881,6037892299063,26901929503849,119887169037291 %N A208040 Number of 4 X n 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 0 and 1 0 1 vertically. %C A208040 Row 4 of A208039. %H A208040 R. H. Hardin, <a href="/A208040/b208040.txt">Table of n, a(n) for n = 1..210</a> %F A208040 Empirical: a(n) = 2*a(n-1) +24*a(n-3) +117*a(n-4) +10*a(n-5) +88*a(n-6) -540*a(n-7) -2784*a(n-8) -648*a(n-9) +880*a(n-10) +2080*a(n-11) +11700*a(n-12) +4200*a(n-13) +2000*a(n-15) -10000*a(n-16). %e A208040 Some solutions for n=4 %e A208040 ..1..1..0..1....1..0..0..1....1..0..0..1....0..1..1..0....0..1..1..0 %e A208040 ..0..1..1..1....1..0..1..1....1..0..1..1....0..1..1..1....1..0..0..1 %e A208040 ..0..0..1..1....0..1..1..1....0..1..1..0....1..0..0..1....1..0..0..1 %e A208040 ..1..0..0..1....0..0..1..1....0..1..1..0....1..0..0..1....1..1..1..1 %Y A208040 Cf. A208039. %K A208040 nonn %O A208040 1,1 %A A208040 _R. H. Hardin_, Feb 22 2012