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 A221317 #6 Jun 02 2025 08:15:29 %S A221317 1,2,7,14,28,66,168,378,866,2128,5065,12000,28866,69652,167994,405058, %T A221317 981305,2381232,5776411,14040684,34175851,83246764,202960219, %U A221317 495273680,1209625253,2956269734,7229756488,17692733704,43322486571,106136686984 %N A221317 Number of nonnegative integer arrays of length n summing to n without equal adjacent values modulo 4. %C A221317 Column 4 of A221321 %H A221317 R. H. Hardin, <a href="/A221317/b221317.txt">Table of n, a(n) for n = 1..210</a> %e A221317 Some solutions for n=7 %e A221317 ..0....2....1....3....0....0....0....1....0....0....2....0....3....1....0....1 %e A221317 ..3....0....3....2....2....1....1....0....1....1....1....5....0....0....2....2 %e A221317 ..0....1....0....0....0....2....0....2....0....0....0....0....1....2....0....1 %e A221317 ..1....3....2....1....1....1....2....1....1....3....1....1....0....0....2....0 %e A221317 ..0....0....0....0....0....0....1....0....0....0....0....0....1....1....1....1 %e A221317 ..1....1....1....1....1....1....0....1....5....3....2....1....0....3....2....0 %e A221317 ..2....0....0....0....3....2....3....2....0....0....1....0....2....0....0....2 %K A221317 nonn %O A221317 1,2 %A A221317 _R. H. Hardin_ Jan 10 2013