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 A203539 #9 May 27 2025 16:40:20 %S A203539 0,64,1840,30976,1700580,46485124,1680210240,56191754304, %T A203539 1898704490980,64488576908484,2178774976790208,73775014607038096, %U A203539 2496772163852959252,84495658280798176036,2859840508384744419504,96787655134946736339600,3275732831885874026239020,110865235815215020663937284 %N A203539 Number of n X 5 0..2 arrays with every element neighboring horizontally or vertically both a 0 and a 1. %H A203539 R. H. Hardin, <a href="/A203539/b203539.txt">Table of n, a(n) for n = 1..210</a> %e A203539 Some solutions for n=5: %e A203539 ..1..0..0..1..1....0..1..2..0..1....2..1..0..0..2....1..1..0..0..0 %e A203539 ..1..2..1..0..0....0..1..2..0..1....0..1..1..1..1....0..1..1..1..1 %e A203539 ..0..1..1..2..1....2..1..2..0..2....0..1..2..2..0....0..1..2..2..1 %e A203539 ..0..2..0..0..1....1..0..0..1..0....0..1..0..1..0....0..0..0..0..0 %e A203539 ..1..1..0..0..1....1..0..1..1..0....1..1..0..1..2....1..1..1..1..0 %Y A203539 Column 5 of A203542. %K A203539 nonn %O A203539 1,2 %A A203539 _R. H. Hardin_, Jan 02 2012