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 A216027 #6 Jul 22 2025 23:29:05 %S A216027 1,5,29,371,6150,167130,5219070,233834847,11412814314,741757937068, %T A216027 51088102234508,4468693984145541,407520605922011467, %U A216027 45668525708806007925,5279748839226156263229,732043230152926700952839 %N A216027 Number of horizontal, vertical and diagonal neighbor colorings of the odd squares of an nX4 array with new integer colors introduced in row major order. %C A216027 Column 4 of A216031 %H A216027 R. H. Hardin, <a href="/A216027/b216027.txt">Table of n, a(n) for n = 1..20</a> %e A216027 Some solutions for n=4 %e A216027 ..x..0..x..1....x..0..x..1....x..0..x..1....x..0..x..1....x..0..x..1 %e A216027 ..1..x..2..x....2..x..1..x....0..x..2..x....0..x..1..x....2..x..1..x %e A216027 ..x..2..x..3....x..3..x..2....x..1..x..0....x..1..x..2....x..1..x..3 %e A216027 ..3..x..4..x....1..x..4..x....3..x..4..x....1..x..3..x....1..x..3..x %K A216027 nonn %O A216027 1,2 %A A216027 _R. H. Hardin_ Aug 30 2012