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 A199828 #7 Jul 22 2025 13:24:01 %S A199828 44,336,2146,15708,118280,888420,6715618,51077518,390278378, %T A199828 2993722414,23038998514,177794832922,1375379617514,10662124449466, %U A199828 82808224932874,644200988262616,5018935818153796,39154328577073846,305823285072243150 %N A199828 Number of -4..4 arrays x(0..n+1) of n+2 elements with zero sum and no two neighbors summing to zero. %C A199828 Column 4 of A199832 %H A199828 R. H. Hardin, <a href="/A199828/b199828.txt">Table of n, a(n) for n = 1..200</a> %e A199828 Some solutions for n=3 %e A199828 ..1...-1....4....0....1....0....0...-1...-3....4...-1...-3....0...-3...-4...-1 %e A199828 .-3...-1....0...-1....3....3...-1...-1....4...-3....4....4...-2....1....3...-1 %e A199828 ..1....0...-2....0....0...-1...-2...-4....1....2...-2...-3...-2....0....4....0 %e A199828 ..3....2....0....3...-4...-3....3....3...-2...-4...-2....4....4....2...-3....3 %e A199828 .-2....0...-2...-2....0....1....0....3....0....1....1...-2....0....0....0...-1 %K A199828 nonn %O A199828 1,1 %A A199828 _R. H. Hardin_ Nov 11 2011