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 A180753 #5 Jul 22 2025 08:28:20 %S A180753 0,2,2,9,21,70,207,658,2059,6521,20602,65244,206608,654594,2073996, %T A180753 6571885,20824917,65991668,209121585,662691890,2100031249,6654888151, %U A180753 21089009696,66830061534,211781324846,671125181554,2126764718766 %N A180753 Half the number of nX4 binary arrays with each element equal to at least two neighbors. %C A180753 Column 4 of A180760 %H A180753 R. H. Hardin, <a href="/A180753/b180753.txt">Table of n, a(n) for n=1..99</a> %F A180753 Empirical: a(n) = 5*a(n-1) - 6*a(n-2) + a(n-3) + a(n-4) - 9*a(n-5) + 4*a(n-6) + a(n-7) + 28*a(n-8) - 16*a(n-9) - 3*a(n-10) + 2*a(n-11) - 6*a(n-12) + 2*a(n-13) - a(n-14) %K A180753 nonn %O A180753 1,2 %A A180753 _R. H. Hardin_ Sep 20 2010