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 A200186 #8 Jul 22 2025 15:43:26 %S A200186 1,4,6,14,24,54,104,230,464,1028,2128,4720,9918,22038,46760,104056, %T A200186 222338,495358,1064138,2373070,5119796,11425974,24738074,55242788, %U A200186 119958510,268018844,583462384,1304179214,2845288284,6362293924 %N A200186 Number of -2..2 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 A200186 Column 2 of A200192 %H A200186 R. H. Hardin, <a href="/A200186/b200186.txt">Table of n, a(n) for n = 1..200</a> %e A200186 Some solutions for n=5 %e A200186 .-2....0...-2....0...-1....2....2...-2...-1...-1...-2....1....1....2...-1....0 %e A200186 ..1....2....2...-2....2...-2...-2....2....2....1....2...-1...-2...-1....2....2 %e A200186 .-1...-2...-1....2...-1....2....0...-2...-1...-1....0....2....1....1...-2...-1 %e A200186 ..2....1....2...-2....1...-2...-2....2....2....2....2...-2...-1...-2....2....1 %e A200186 ..0...-1...-1....2...-1....0....2....0...-2...-1...-2....0....1....0...-1...-2 %K A200186 nonn %O A200186 1,2 %A A200186 _R. H. Hardin_ Nov 14 2011