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 A216340 #6 Jul 22 2025 23:31:08 %S A216340 2,10,52,726,12840,373780,12297870,580853761,29562890980, %T A216340 2004648246554,142953068558998,12954739605661928,1216988850964527370, %U A216340 140585911310155419266,16679506383419809650408,2374936932537133281235971 %N A216340 Number of horizontal and antidiagonal neighbor colorings of the even squares of a 4Xn array with new integer colors introduced in row major order. %C A216340 Row 4 of A216338 %H A216340 R. H. Hardin, <a href="/A216340/b216340.txt">Table of n, a(n) for n = 1..19</a> %e A216340 Some solutions for n=4 %e A216340 ..0..x..1..x....0..x..1..x....0..x..1..x....0..x..1..x....0..x..1..x %e A216340 ..x..2..x..3....x..2..x..3....x..2..x..3....x..0..x..1....x..2..x..3 %e A216340 ..4..x..0..x....4..x..5..x....3..x..1..x....2..x..3..x....0..x..2..x %e A216340 ..x..5..x..3....x..3..x..0....x..3..x..1....x..2..x..1....x..0..x..4 %K A216340 nonn %O A216340 1,1 %A A216340 _R. H. Hardin_ Sep 04 2012