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 A268940 #8 Jan 17 2019 02:51:37 %S A268940 5,25,120,565,2615,11950,54045,242365,1079240,4777225,21038595, %T A268940 92244790,402898865,1753806625,7611458520,32945585965,142262759615, %U A268940 612991045150,2636186279445,11317111447765,48506655275240,207603081203425 %N A268940 Number of length-n 0..4 arrays with no repeated value unequal to the previous repeated value plus one mod 4+1. %H A268940 R. H. Hardin, <a href="/A268940/b268940.txt">Table of n, a(n) for n = 1..210</a> %F A268940 Empirical: a(n) = 7*a(n-1) - 7*a(n-2) - 20*a(n-3). %F A268940 Empirical g.f.: 5*x*(1 - 2*x - 4*x^2) / ((1 - 4*x)*(1 - 3*x - 5*x^2)). - _Colin Barker_, Jan 17 2019 %e A268940 Some solutions for n=7: %e A268940 ..2. .0. .3. .2. .2. .4. .1. .2. .3. .2. .2. .1. .1. .1. .3. .2 %e A268940 ..3. .4. .3. .1. .3. .0. .3. .1. .3. .4. .0. .0. .2. .4. .0. .1 %e A268940 ..1. .3. .0. .3. .2. .3. .1. .3. .2. .4. .3. .1. .4. .1. .2. .1 %e A268940 ..3. .4. .1. .1. .0. .4. .4. .1. .1. .3. .2. .2. .1. .1. .1. .4 %e A268940 ..4. .0. .4. .4. .0. .0. .1. .4. .4. .4. .0. .2. .2. .4. .4. .1 %e A268940 ..0. .0. .0. .0. .1. .2. .3. .3. .1. .3. .4. .4. .4. .0. .2. .4 %e A268940 ..1. .3. .2. .1. .4. .3. .4. .3. .4. .0. .1. .0. .0. .2. .2. .0 %Y A268940 Column 4 of A268944. %K A268940 nonn %O A268940 1,1 %A A268940 _R. H. Hardin_, Feb 16 2016