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 A180764 #5 Jul 22 2025 08:29:27 %S A180764 2,34,390,4475,52186,606546,7053923,82032712,953982820,11094190209, %T A180764 129018028226,1500393683522,17448578663219,202915341402216, %U A180764 2359770191311572,27442554696574793,319138622503858354 %N A180764 Half the number of nX4 binary arrays with each element equal to at least one neighbor. %C A180764 Column 4 of A180771 %H A180764 R. H. Hardin, <a href="/A180764/b180764.txt">Table of n, a(n) for n=1..99</a> %F A180764 Empirical: a(n) = 9*a(n-1) + 35*a(n-2) - 29*a(n-3) - 256*a(n-4) - 120*a(n-5) + 695*a(n-6) + 579*a(n-7) - 949*a(n-8) - 1076*a(n-9) + 485*a(n-10) + 1488*a(n-11) + 588*a(n-12) - 857*a(n-13) - 368*a(n-14) - 73*a(n-15) - 52*a(n-16) + 26*a(n-17) + 14*a(n-18) + 12*a(n-19) - 4*a(n-20) %K A180764 nonn %O A180764 1,1 %A A180764 _R. H. Hardin_ Sep 20 2010