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 A188352 #7 Jul 22 2025 11:09:28 %S A188352 13,91,257,1775,7369,49747,262925,1763151,10536621,70819767,449413269, %T A188352 3032790187,19849674769,134432007295,895147297233,6080318813363, %U A188352 40910518802585,278583012405979,1887082800975125,12878423767271251 %N A188352 Number of arrangements of n+1 numbers x(i) in -3..3 with the sum of x(i)*x(i+1) equal to zero. %C A188352 Column 3 of A188358 %H A188352 R. H. Hardin, <a href="/A188352/b188352.txt">Table of n, a(n) for n = 1..124</a> %e A188352 Some solutions for n=4 %e A188352 .-1....2...-2...-1...-3....2....0...-3....0....1....2....3....1....2....1....0 %e A188352 ..0...-3....0....0....2...-2....0....1....0....3...-2...-1...-3....0....3....0 %e A188352 ..3....0...-1...-2...-2...-2....3....2....2...-1...-2....1...-1....3....0...-2 %e A188352 ..0....2....0...-2...-2....0....1....1...-1....0...-3...-2....0....0....1...-3 %e A188352 ..0....3....1....2...-3...-3...-3...-1...-2....0....2...-3....2...-1...-3....2 %K A188352 nonn %O A188352 1,1 %A A188352 _R. H. Hardin_ Mar 28 2011