%I #4 Feb 16 2016 11:52:33
%S 5,29,138,634,3045,15579,85314,498408,3092383,20286281,140153290,
%T 1016261974,7710988251,61062381647,503482376776,4313580705556,
%U 38328590370571,352618807558797,3353663977088616,32927374589861042
%N 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 Subdiagonal 3 of A268956.
%H R. H. Hardin, <a href="/A268957/b268957.txt">Table of n, a(n) for n = 1..119</a>
%e Some solutions for n=7
%e ..0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0. .0
%e ..1. .1. .0. .1. .1. .1. .1. .0. .0. .1. .1. .1. .1. .1. .1. .0
%e ..2. .2. .1. .1. .2. .2. .2. .1. .1. .2. .0. .2. .2. .2. .2. .1
%e ..3. .3. .2. .0. .3. .2. .0. .2. .2. .3. .0. .3. .2. .0. .1. .2
%e ..0. .3. .3. .2. .4. .3. .3. .1. .0. .1. .2. .3. .3. .1. .1. .0
%e ..0. .0. .4. .3. .5. .1. .0. .2. .3. .0. .1. .4. .4. .0. .3. .3
%e ..1. .4. .4. .2. .1. .4. .4. .1. .0. .1. .3. .0. .4. .3. .1. .1
%e ..1. .5. .2. .0. .1. .4. .3. .3. .3. .3. .4. .5. .2. .4. .3. .1
%e ..3. .1. .5. .2. .5. .3. .1. .0. .0. .1. .0. .3. .2. .5. .1. .2
%e ..0. .0. .4. .1. .5. .1. .2. .2. .4. .4. .4. .2. .1. .3. .0. .2
%Y Cf. A268956.
%K nonn
%O 1,1
%A _R. H. Hardin_, Feb 16 2016