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 A202247 #7 Jun 02 2025 07:24:42 %S A202247 1,3,17,81,397,2003,10239,52697,273021,1422337,7442827,39091861, %T A202247 205972443,1088212379,5762943375,30582601227,162591973175, %U A202247 865826349887,4617379607829,24656446918287,131820057982369,705507882790695 %N A202247 Number of zero-sum -3..3 arrays of n elements with adjacent element differences also in -3..3. %C A202247 Column 3 of A202252 %H A202247 R. H. Hardin, <a href="/A202247/b202247.txt">Table of n, a(n) for n = 1..210</a> %e A202247 Some solutions for n=8 %e A202247 .-1...-3....2...-2...-3....0....3....0...-1...-2...-1....3...-2...-1....2....3 %e A202247 .-3...-3....3....1...-3....0....2....2....2....0....1....3....0....1...-1....0 %e A202247 ..0....0....1...-2....0...-2....2....0....0....0...-2....0....0...-1...-3....3 %e A202247 ..2....3....1....1....2....0....0...-1....1....1....0....0...-3...-1....0....1 %e A202247 ..1....0...-2....0...-1....0...-3...-1...-1....2....0...-2....0....0....1...-2 %e A202247 ..0....1...-2....1....0....1...-2....1....2....0....0....0....2....0....1....0 %e A202247 ..0....1...-1....2....3....1...-2...-2...-1....1....0...-2....2....1...-1...-3 %e A202247 ..1....1...-2...-1....2....0....0....1...-2...-2....2...-2....1....1....1...-2 %K A202247 nonn %O A202247 1,2 %A A202247 _R. H. Hardin_ Dec 14 2011