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 A200188 #7 Jul 22 2025 15:43:39 %S A200188 1,8,28,120,506,2240,9856,44562,199932,914676,4152696,19143782, %T A200188 87622590,406118090,1869888346,8701509206,40245967276,187867050760, %U A200188 872020225984,4080661245080,18995817588580,89071683414448,415623180115020 %N A200188 Number of -4..4 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 A200188 Column 4 of A200192 %H A200188 R. H. Hardin, <a href="/A200188/b200188.txt">Table of n, a(n) for n = 1..200</a> %e A200188 Some solutions for n=5 %e A200188 ..1....2....1...-1....4....0...-2...-1....0...-4...-2....0....3....4....0....2 %e A200188 ..4...-1...-4....4...-3....4....2...-3....3....3...-4...-3...-4...-4...-4...-2 %e A200188 .-3....2....2...-2....4...-2...-3....4...-2....1....3....2....4....0....3....2 %e A200188 ..1...-3...-1....3...-4....1....4...-1....2....3....0...-1...-3...-3...-2...-2 %e A200188 .-3....0....2...-4...-1...-3...-1....1...-3...-3....3....2....0....3....3....0 %K A200188 nonn %O A200188 1,2 %A A200188 _R. H. Hardin_ Nov 14 2011