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 A186163 #7 Jul 22 2025 10:17:04 %S A186163 4,321,14364,751266,37402872,1899336597,95752776009,4840082975532, %T A186163 244420512852030,12347377339339755,623671780419814416, %U A186163 31503432697236966789,1591300459563274835532,80380228276030331585859 %N A186163 1/4 the number of nX4 0..3 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors. %C A186163 Column 4 of A186168 %H A186163 R. H. Hardin, <a href="/A186163/b186163.txt">Table of n, a(n) for n = 1..200</a> %e A186163 Some solutions for 6X4 with a(1,1)=0 %e A186163 ..0..0..0..1....0..0..2..2....0..0..0..3....0..0..1..1....0..0..3..3 %e A186163 ..0..2..2..1....0..2..2..1....0..2..2..3....0..2..2..1....0..2..2..2 %e A186163 ..0..0..2..3....0..0..1..1....0..0..3..0....0..0..1..1....0..0..3..1 %e A186163 ..2..0..0..3....2..0..2..2....2..0..3..0....2..0..3..3....2..0..3..1 %e A186163 ..2..2..0..0....2..3..3..1....2..2..2..0....2..2..2..2....2..0..2..2 %e A186163 ..0..0..2..2....0..0..0..1....0..0..1..1....0..0..1..1....2..2..0..0 %K A186163 nonn %O A186163 1,1 %A A186163 _R. H. Hardin_ Feb 13 2011