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 A200187 #7 Jul 22 2025 15:43:33 %S A200187 1,6,14,48,144,482,1534,5148,16826,56918,188706,642300,2149072, %T A200187 7348408,24749244,84919630,287439908,988917344,3360535304,11586463472, %U A200187 39498606276,136421151864,466287543690,1612808711870,5524756100592 %N A200187 Number of -3..3 arrays x(0..n-1) of n elements with zero sum, adjacent elements differing by more than one, and elements alternately increasing and decreasing. %C A200187 Column 3 of A200192 %H A200187 R. H. Hardin, <a href="/A200187/b200187.txt">Table of n, a(n) for n = 1..200</a> %e A200187 Some solutions for n=5 %e A200187 ..3...-2...-1...-2...-1...-2....2...-2....0....2....2...-1...-3....3....0....2 %e A200187 .-3....3....3....2...-3....2...-2....2...-2...-3...-3....2....2...-3....2...-2 %e A200187 ..0...-3...-3....0....2...-2....2....0....2....3....1...-1...-3....2...-3....1 %e A200187 .-3....2....3....2...-1....2...-3....3...-2...-2...-2....1....3...-3....3...-3 %e A200187 ..3....0...-2...-2....3....0....1...-3....2....0....2...-1....1....1...-2....2 %K A200187 nonn %O A200187 1,2 %A A200187 _R. H. Hardin_ Nov 14 2011