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%I
%S 2,6,24,118,686,4598,34872,295044,2753958,28103804,311216626,
%T 3716341042,47597786154,650812077852,9461423560788,145724617925326,
%U 2370293673319292,40600119927220706,730458115445479734,13772063820971722638
%N Number of length n arrays x(i), i=1..n with x(i) in 0..i and no value appearing more than 3 times
%C Column 3 of A248842.
%C Essentially the same as A135106. - _Georg Fischer_, Oct 23 2018
%H R. H. Hardin, <a href="/A248837/b248837.txt">Table of n, a(n) for n = 1..210</a>
%e Some solutions for n=6
%e ..0....1....0....1....0....0....1....1....1....0....0....0....0....0....0....1
%e ..2....1....0....2....1....1....1....1....1....1....1....0....0....0....1....1
%e ..2....0....0....0....1....1....2....2....0....3....0....2....3....3....2....2
%e ..1....0....3....0....0....1....4....4....1....0....1....1....2....4....4....1
%e ..5....0....2....2....3....4....5....2....2....4....4....0....1....0....5....5
%e ..3....5....3....1....5....2....5....2....5....0....2....5....0....2....0....6
%K nonn
%O 1,1
%A _R. H. Hardin_, Oct 15 2014
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