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 A188354 #7 Jul 22 2025 11:09:42 %S A188354 21,231,749,8051,45801,480363,3882729,40629247,383541193,4033546763, %T A188354 40584302909,428984471067,4442125791917,47152504083651, %U A188354 495572482473621,5279048333736159,55969066137457201,598015958507349743 %N A188354 Number of arrangements of n+1 numbers x(i) in -5..5 with the sum of x(i)*x(i+1) equal to zero. %C A188354 Column 5 of A188358 %H A188354 R. H. Hardin, <a href="/A188354/b188354.txt">Table of n, a(n) for n = 1..39</a> %e A188354 Some solutions for n=4 %e A188354 ..1...-4...-5...-4....3....5....5....1...-5...-4....0...-5...-1....5...-3....1 %e A188354 ..0...-4....3...-5....5...-1...-4...-2...-3...-4....0....0....0....2....2....4 %e A188354 ..2...-3....3....3...-3....4....3...-4....1....4....4....3....0...-5....5....5 %e A188354 .-2....4....2...-1....5....3....4....2...-4....0....0...-1....0....4...-2...-3 %e A188354 .-2...-4....0....2....3...-1....5....1....2...-2...-5...-3....2....5...-3....3 %K A188354 nonn %O A188354 1,1 %A A188354 _R. H. Hardin_ Mar 28 2011