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 A188353 #7 Jul 22 2025 11:09:35 %S A188353 17,153,497,4201,22229,181449,1264985,10396729,81850801,684867741, %T A188353 5680170701,48268778269,410276328441,3525682027185,30364372592101, %U A188353 262996695840081,2283098828435689,19886474577091625,173553193860930897 %N A188353 Number of arrangements of n+1 numbers x(i) in -4..4 with the sum of x(i)*x(i+1) equal to zero. %C A188353 Column 4 of A188358 %H A188353 R. H. Hardin, <a href="/A188353/b188353.txt">Table of n, a(n) for n = 1..60</a> %e A188353 Some solutions for n=5 %e A188353 ..0...-1...-1....0....0....0....0....0....1...-1....3....3...-1....2...-4....1 %e A188353 ..2...-4...-3....0...-1....0...-4....4...-2...-1....2...-1....2....2...-1...-3 %e A188353 ..1....4...-3....4...-3....4...-2...-1....0....1...-1...-3...-2...-4....4....3 %e A188353 ..1....3....4....0....4...-1....4....0...-2....2....0....0...-3...-4....0....3 %e A188353 .-3...-3...-4....0....3...-2....0....1....1....1...-1....4....3....2....1....3 %e A188353 ..0...-3...-4....4...-1...-1....3....4....4...-4....4....0....3...-2....0...-2 %K A188353 nonn %O A188353 1,1 %A A188353 _R. H. Hardin_ Mar 28 2011