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 A221458 #6 Jul 23 2025 01:57:20 %S A221458 0,1,2,7,25,102,456,2219,11639,65320,389533,2451393,16164044, %T A221458 110866328,785411383,5709898562,42358751505,319155928942, %U A221458 2433165471304,18714220718157,144885627697659,1127182676182780,8800901309557829 %N A221458 Number of 0..7 arrays of length n with each element unequal to at least one neighbor, with new values introduced in 0..7 order. %C A221458 Column 7 of A221459 %H A221458 R. H. Hardin, <a href="/A221458/b221458.txt">Table of n, a(n) for n = 1..210</a> %F A221458 Empirical: a(n) = 22*a(n-1) -168*a(n-2) +440*a(n-3) +421*a(n-4) -2898*a(n-5) -924*a(n-6) +7944*a(n-7) +5931*a(n-8) -6610*a(n-9) -10562*a(n-10) -5040*a(n-11) -840*a(n-12) %e A221458 Some solutions for n=6 %e A221458 ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0 %e A221458 ..1....1....1....1....1....1....1....1....1....1....1....1....1....1....1....1 %e A221458 ..2....1....1....2....0....2....0....0....2....1....1....0....2....2....0....2 %e A221458 ..3....2....0....3....1....2....1....2....0....2....2....0....0....2....0....1 %e A221458 ..0....1....0....3....2....1....2....2....3....0....2....2....1....3....2....1 %e A221458 ..2....0....2....2....1....0....3....1....4....3....0....0....0....1....1....0 %K A221458 nonn %O A221458 1,3 %A A221458 _R. H. Hardin_ Jan 17 2013