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 A203485 #8 May 23 2023 12:14:17 %S A203485 6,10,36,82,256,676,2050,5826,17568,51640,155590,463996,1397766, %T A203485 4192646,12626836,37955426,114267376,343694728,1034313190,3111132672, %U A203485 9359196778,28146901826,84646727920,254509346220,765178882006,2300166018706 %N A203485 Number of n X 2 0..2 arrays with row sums equal and column sums unequal to adjacent columns. %C A203485 Column 2 of A203491. %H A203485 R. H. Hardin, <a href="/A203485/b203485.txt">Table of n, a(n) for n = 1..210</a> %e A203485 Some solutions for n=5 %e A203485 ..2..0....2..0....1..0....2..0....0..2....0..2....1..0....2..0....2..0....0..1 %e A203485 ..1..1....0..2....0..1....2..0....2..0....1..1....0..1....1..1....1..1....0..1 %e A203485 ..0..2....0..2....0..1....2..0....0..2....0..2....1..0....1..1....0..2....1..0 %e A203485 ..2..0....0..2....0..1....2..0....0..2....0..2....0..1....0..2....2..0....0..1 %e A203485 ..1..1....2..0....0..1....0..2....1..1....0..2....1..0....2..0....2..0....0..1 %Y A203485 Cf. A203491. %K A203485 nonn %O A203485 1,1 %A A203485 _R. H. Hardin_, Jan 02 2012