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Number of length n+6 0..3 arrays with at most one downstep in every 6 consecutive neighbor pairs
1

%I #4 Jun 08 2015 11:51:13

%S 2592,5664,13720,35704,92548,228081,526672,1183616,2727288,6597449,

%T 16454876,40863000,98379104,230053160,534172704,1260245516,3043544240,

%U 7443617220,18093595536,43272115712,102190186552,241107878575

%N Number of length n+6 0..3 arrays with at most one downstep in every 6 consecutive neighbor pairs

%C Column 6 of A258730

%H R. H. Hardin, <a href="/A258728/b258728.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 4*a(n-1) -6*a(n-2) +4*a(n-3) -a(n-4) +80*a(n-6) -204*a(n-7) +177*a(n-8) -52*a(n-9) -125*a(n-12) +184*a(n-13) -68*a(n-14) +10*a(n-18) -4*a(n-19)

%e Some solutions for n=4

%e ..0....3....0....3....3....1....0....2....0....0....1....0....0....3....3....1

%e ..3....3....0....3....3....2....1....0....3....2....1....2....2....3....1....2

%e ..0....0....2....0....1....3....0....1....3....0....0....2....0....1....1....0

%e ..0....2....3....0....1....3....0....2....3....0....0....2....0....1....2....1

%e ..0....2....0....0....2....1....1....3....3....1....0....2....1....1....3....2

%e ..0....2....0....1....2....1....2....3....3....1....3....1....2....1....3....2

%e ..1....3....0....2....2....1....2....3....3....1....3....1....2....1....3....3

%e ..3....3....2....2....3....1....3....3....0....1....3....1....3....1....0....3

%e ..2....3....3....0....1....2....2....1....1....2....0....1....3....3....1....0

%e ..2....3....3....1....3....3....3....3....2....2....1....1....0....1....1....2

%Y Cf. A258730

%K nonn

%O 1,1

%A _R. H. Hardin_, Jun 08 2015