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 A206891 #7 Jul 22 2025 19:47:21 %S A206891 20,400,4792,51800,607043,7354488,88342972,1052865902,12550021410, %T A206891 149829237791,1789228772267,21361035307546,254996432939040, %U A206891 3044109171852296,36341089959264948,433845306322806048 %N A206891 Number of 5Xn 0..1 arrays avoiding 0 1 0 horizontally and 1 0 0 vertically. %C A206891 Row 5 of A206889 %H A206891 R. H. Hardin, <a href="/A206891/b206891.txt">Table of n, a(n) for n = 1..210</a> %e A206891 Some solutions for n=4 %e A206891 ..0..1..1..0....1..0..1..1....0..0..1..1....1..1..1..1....1..0..1..1 %e A206891 ..1..1..0..1....1..1..1..1....0..0..1..1....1..1..0..0....1..0..1..1 %e A206891 ..0..0..1..1....0..1..1..1....1..0..0..0....0..0..1..1....0..0..0..0 %e A206891 ..1..1..1..0....1..1..0..0....0..1..1..1....1..1..0..0....1..0..1..1 %e A206891 ..0..1..1..1....0..1..1..1....1..0..1..1....1..0..1..1....1..1..0..1 %K A206891 nonn %O A206891 1,1 %A A206891 _R. H. Hardin_ Feb 13 2012