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 A221315 #7 Jun 02 2025 08:15:22 %S A221315 1,0,3,8,5,0,28,72,45,0,286,728,455,0,3060,7752,4845,0,33649,85008, %T A221315 53130,0,376740,950040,593775,0,4272048,10759232,6724520,0,48903492, %U A221315 123047496,76904685,0,563921995,1417861016,886163135,0,6540715896,16435645072 %N A221315 Number of nonnegative integer arrays of length n summing to n without equal adjacent values modulo 2. %C A221315 Column 2 of A221321 %C A221315 Solutions must alternate even-odd, and cannot have an odd number of those pairs for even n, so a(n)=0 for n modulo 4 = 2 %H A221315 R. H. Hardin, <a href="/A221315/b221315.txt">Table of n, a(n) for n = 1..210</a> %e A221315 All solutions for n=5 %e A221315 ..1....1....1....1....3 %e A221315 ..0....0....0....2....0 %e A221315 ..3....1....1....1....1 %e A221315 ..0....0....2....0....0 %e A221315 ..1....3....1....1....1 %K A221315 nonn %O A221315 1,3 %A A221315 _R. H. Hardin_ Jan 10 2013