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 A199524 #8 Jul 22 2025 13:19:39 %S A199524 1,4,18,72,320,1414,6346,28766,131246,602390,2777638,12857572, %T A199524 59712940,278096674,1298309782,6074112952,28470828008,133671581490, %U A199524 628526085270,2959291856816,13950087683416,65832860408434,310987879638926 %N A199524 Number of -2..2 arrays x(0..n-1) of n elements with zero sum and no two consecutive zero elements. %C A199524 Column 2 of A199530 %H A199524 R. H. Hardin, <a href="/A199524/b199524.txt">Table of n, a(n) for n = 1..200</a> %e A199524 Some solutions for n=5 %e A199524 .-1....2....0...-1...-1....1...-2....2....1....1....0....0...-2....0...-1...-1 %e A199524 ..0....1...-2....2....2....1....2...-2....0....2...-1....1....1....1....0...-2 %e A199524 .-2...-2....1....2....2....1...-2....2....1...-1...-1....1....2...-2....2....0 %e A199524 ..1...-1....0...-2...-1...-2....2....0...-2....0....0...-1....1....2....1....2 %e A199524 ..2....0....1...-1...-2...-1....0...-2....0...-2....2...-1...-2...-1...-2....1 %K A199524 nonn %O A199524 1,2 %A A199524 _R. H. Hardin_ Nov 07 2011