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 A199842 #8 Dec 02 2014 09:00:26 %S A199842 1,4,13,42,132,428,1393,4561,15032,49889,166542,558744,1883028, %T A199842 6370957,21628455,73641852,251385571,860067894,2948380732,10124956970, %U A199842 34823894885,119940097035,413612099138,1427945022753,4934850614704 %N A199842 Number of -3..3 arrays x(0..n-1) of n elements with zero sum and no element more than one greater than the previous. %C A199842 Column 3 of A199847. %H A199842 R. H. Hardin, <a href="/A199842/b199842.txt">Table of n, a(n) for n = 1..200</a> %e A199842 Some solutions for n=6 %e A199842 ..0...-1....3....1....3....0....3....3....1....1....2....3....0....1....0....2 %e A199842 ..1....0....2....1....0....0....0....0....1....1....2....1....1....0....0....3 %e A199842 ..1....1....2...-1...-2....0....1....1....0...-1....2....2....2....1....1....1 %e A199842 .-1....1...-2....0...-1....0....0...-1....0...-1...-1...-1...-1....2....2...-1 %e A199842 ..0....0...-3...-1....0....1...-2...-2....0....0...-2...-3....0...-2...-1...-2 %e A199842 .-1...-1...-2....0....0...-1...-2...-1...-2....0...-3...-2...-2...-2...-2...-3 %K A199842 nonn %O A199842 1,2 %A A199842 _R. H. Hardin_, Nov 11 2011