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 A201807 #11 May 02 2025 03:54:24 %S A201807 1,9,25,313,1401,15681,90609,909945,6105913,57290209,421304049, %T A201807 3799765201,29595440785,261111392985,2109792275145,18400232046585, %U A201807 152275971653625,1320864136716225,11107129707193809,96160509723165393,817518139811725713,7077960886109335737,60642227399014653225 %N A201807 Number of arrays of n integers in -4..4 with sum zero and equal numbers of elements greater than zero and less than zero. %H A201807 R. H. Hardin, <a href="/A201807/b201807.txt">Table of n, a(n) for n = 1..210</a> %e A201807 Some solutions for n=7: %e A201807 .-3....0...-1....4...-2...-4....4...-2....4....4...-3....2....4...-4....1....2 %e A201807 ..0....2....2...-4...-2...-4...-4...-1....0....0....0...-4....0...-4...-3...-3 %e A201807 .-4...-4....1...-4....2....4...-3...-4...-3...-4...-2....3....2...-2....1...-4 %e A201807 ..2...-2....0....0....2....0....0....2...-2....1....4...-3...-4....0...-1....0 %e A201807 .-2....4....3...-2...-1....3...-2....4....3...-3...-4....4....4....2....4...-2 %e A201807 ..4....1...-1....3....1...-3....4....0....1...-2....3...-2...-2....4...-2....4 %e A201807 ..3...-1...-4....3....0....4....1....1...-3....4....2....0...-4....4....0....3 %Y A201807 Column 4 of A201811. %K A201807 nonn %O A201807 1,2 %A A201807 _R. H. Hardin_, Dec 05 2011