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 A199830 #7 Jul 22 2025 13:24:16 %S A199830 102,1144,11384,124982,1402934,15805218,179213048,2044221894, %T A199830 23427591518,269528370904,3111004900884,36009192415678, %U A199830 417810425670462,4858093196583212,56593178356427376,660363780853262084 %N A199830 Number of -6..6 arrays x(0..n+1) of n+2 elements with zero sum and no two neighbors summing to zero. %C A199830 Column 6 of A199832 %H A199830 R. H. Hardin, <a href="/A199830/b199830.txt">Table of n, a(n) for n = 1..200</a> %e A199830 Some solutions for n=3 %e A199830 ..0....3....6...-4....0...-6...-1....6...-1...-2...-3....0....1...-6...-2....4 %e A199830 .-2....5...-5...-6....3....3...-5....1....6....4....5...-6....0....3...-3...-3 %e A199830 ..1...-4...-5....3...-2...-2....2....0...-3...-5....6...-1...-4....0....0...-5 %e A199830 ..2...-4...-1....4...-1....5....1...-3....4...-1...-3....6....2....6....2....4 %e A199830 .-1....0....5....3....0....0....3...-4...-6....4...-5....1....1...-3....3....0 %K A199830 nonn %O A199830 1,1 %A A199830 _R. H. Hardin_ Nov 11 2011