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 A188359 #7 Jul 22 2025 11:10:09 %S A188359 29,117,257,497,749,1205,1569,2161,2765,3589,4177,5377,6077,7253,8561, %T A188359 10017,10941,12837,13873,16017,17933,19845,21105,24097,25981,28245, %U A188359 30593,33729,35325,39397,41105,44449,47517,50517,53905,59009,61053,64405,68033 %N A188359 Number of arrangements of 4 numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero. %C A188359 Row 3 of A188358 %H A188359 R. H. Hardin, <a href="/A188359/b188359.txt">Table of n, a(n) for n = 1..135</a> %e A188359 Some solutions for n=4 %e A188359 ..0....2...-3....3....2....3....0...-2....4...-1...-3....0....3...-4...-4....2 %e A188359 .-2....0....2...-2....0....0....1....0....0...-2...-2....4....0....0....3....0 %e A188359 ..0....0....3....3....3...-1....0....0...-3....1....3....0....3....2....4...-3 %e A188359 .-3...-2....0....4....0....0....1...-3....0....0....0...-1....0....0....0....0 %K A188359 nonn %O A188359 1,1 %A A188359 _R. H. Hardin_ Mar 28 2011