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 A268957 #4 Feb 16 2016 11:52:33 %S A268957 5,29,138,634,3045,15579,85314,498408,3092383,20286281,140153290, %T A268957 1016261974,7710988251,61062381647,503482376776,4313580705556, %U A268957 38328590370571,352618807558797,3353663977088616,32927374589861042 %N A268957 Number of length-(n+3) 0..n arrays with no repeated value equal to the previous repeated value, with new values introduced in sequential order. %C A268957 Subdiagonal 3 of A268956. %H A268957 R. H. Hardin, <a href="/A268957/b268957.txt">Table of n, a(n) for n = 1..119</a> %e A268957 Some solutions for n=7 %e A268957 ..0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0 %e A268957 ..1. .1. .0. .1. .1. .1. .1. .0. .0. .1. .1. .1. .1. .1. .1. .0 %e A268957 ..2. .2. .1. .1. .2. .2. .2. .1. .1. .2. .0. .2. .2. .2. .2. .1 %e A268957 ..3. .3. .2. .0. .3. .2. .0. .2. .2. .3. .0. .3. .2. .0. .1. .2 %e A268957 ..0. .3. .3. .2. .4. .3. .3. .1. .0. .1. .2. .3. .3. .1. .1. .0 %e A268957 ..0. .0. .4. .3. .5. .1. .0. .2. .3. .0. .1. .4. .4. .0. .3. .3 %e A268957 ..1. .4. .4. .2. .1. .4. .4. .1. .0. .1. .3. .0. .4. .3. .1. .1 %e A268957 ..1. .5. .2. .0. .1. .4. .3. .3. .3. .3. .4. .5. .2. .4. .3. .1 %e A268957 ..3. .1. .5. .2. .5. .3. .1. .0. .0. .1. .0. .3. .2. .5. .1. .2 %e A268957 ..0. .0. .4. .1. .5. .1. .2. .2. .4. .4. .4. .2. .1. .3. .0. .2 %Y A268957 Cf. A268956. %K A268957 nonn %O A268957 1,1 %A A268957 _R. H. Hardin_, Feb 16 2016