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 A188326 #7 Jul 22 2025 11:07:39 %S A188326 0,2,4,20,86,424,2128,11200,60372,333254,1872728,10688284,61792756, %T A188326 361247006,2132290212,12692489494,76115308712,459476777038, %U A188326 2790092370660,17032567789840,104478722395496,643682329681246,3981493201581658 %N A188326 Number of nondecreasing arrangements of n nonzero numbers in -n..n with sum zero. %C A188326 Column 2 of A188333 %H A188326 R. H. Hardin, <a href="/A188326/b188326.txt">Table of n, a(n) for n = 1..31</a> %e A188326 Some solutions for n=6 %e A188326 .-6...-4...-6...-4...-4...-5...-6...-4...-6...-4...-6...-6...-5...-6...-5...-3 %e A188326 .-5...-4...-3...-1...-3...-2...-5...-3...-6...-4...-3...-6...-4...-5...-4...-1 %e A188326 ..1...-2...-3...-1...-2...-2...-2...-2...-3...-1....2....2...-3....1...-2...-1 %e A188326 ..1....3....3...-1...-1....1....3...-2....3...-1....2....2....2....2....2...-1 %e A188326 ..4....3....4....2....4....2....4....5....6....5....2....3....5....3....3....1 %e A188326 ..5....4....5....5....6....6....6....6....6....5....3....5....5....5....6....5 %K A188326 nonn %O A188326 1,2 %A A188326 _R. H. Hardin_ Mar 28 2011