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 A199698 #10 Jul 22 2025 13:22:20 %S A199698 1,4,14,52,200,708,2642,10000,37984,144876,554120,2128672,8204180, %T A199698 31697564,122734614,476170124,1850664202,7204005752,28081918548, %U A199698 109604285492,428278469018,1675246478864,6559126501510,25703606447364 %N A199698 Number of -2..2 arrays x(0..n-1) of n elements with zero sum and no two neighbors equal. %C A199698 Column 2 of A199704 %H A199698 R. H. Hardin, <a href="/A199698/b199698.txt">Table of n, a(n) for n = 1..200</a> %e A199698 Some solutions for n=5 %e A199698 ..0....1...-2....0....2...-1....2....2....1....2...-1....2....1....0....2....0 %e A199698 .-1....0....2....1...-2....1....1....0...-1...-2....1...-1....2...-1...-1...-1 %e A199698 ..1...-1...-1...-2....1...-1...-1...-1....0....0....0....1...-2....1....1....2 %e A199698 .-1...-2....0....0...-1....1...-2....1...-2...-1...-1....0...-1....2...-2...-1 %e A199698 ..1....2....1....1....0....0....0...-2....2....1....1...-2....0...-2....0....0 %K A199698 nonn %O A199698 1,2 %A A199698 _R. H. Hardin_ Nov 09 2011