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 A188230 #7 Jul 22 2025 11:03:46 %S A188230 1,4,12,52,221,1019,4818,23522,117209,594789,3062414,15966168, %T A188230 84132345,447457816,2399177028,12956403904,70416558196,384897011042, %U A188230 2114694606220,11672750655842,64705139473661,360068911514032,2010827078176568 %N A188230 Number of nondecreasing arrangements of n numbers in -(n+1)..(n+1) with sum zero and not more than two numbers equal. %C A188230 Column 3 of A188236 %H A188230 R. H. Hardin, <a href="/A188230/b188230.txt">Table of n, a(n) for n = 1..30</a> %e A188230 Some solutions for n=4 %e A188230 .-3...-5...-5...-3...-3...-1...-4...-5...-4...-4...-2...-5...-4...-4...-4...-3 %e A188230 .-2...-5....0...-3....0...-1....1...-1...-2...-4...-2...-3...-1...-3...-3...-1 %e A188230 ..1....5....1....2....1....0....1....2....2....3....1....3....2....2....3....2 %e A188230 ..4....5....4....4....2....2....2....4....4....5....3....5....3....5....4....2 %K A188230 nonn %O A188230 1,2 %A A188230 _R. H. Hardin_ Mar 24 2011