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A268453 Number of length-n 0..4 arrays with no adjacent pair x,x+1 followed at any distance by x+1,x.

%I A268453 #4 Feb 04 2016 22:01:29
%S A268453 5,25,121,581,2776,13204,62535,294967,1385969,6488635,30273074,
%T A268453 140779986,652648100,3016745162,13905372533,63924885355,293126854872,
%U A268453 1340883359460,6119617278729,27867658231717,126637380509476,574312506857594
%N A268453 Number of length-n 0..4 arrays with no adjacent pair x,x+1 followed at any distance by x+1,x.
%C A268453 Column 4 of A268457.
%H A268453 R. H. Hardin, <a href="/A268453/b268453.txt">Table of n, a(n) for n = 1..210</a>
%F A268453 Empirical: a(n) = 39*a(n-1) -693*a(n-2) +7441*a(n-3) -54053*a(n-4) +282341*a(n-5) -1103223*a(n-6) +3324255*a(n-7) -7938129*a(n-8) +15426103*a(n-9) -25019179*a(n-10) +34622055*a(n-11) -41606078*a(n-12) +43991906*a(n-13) -41304450*a(n-14) +34649044*a(n-15) -26064185*a(n-16) +17607461*a(n-17) -10675286*a(n-18) +5792770*a(n-19) -2798790*a(n-20) +1194342*a(n-21) -444872*a(n-22) +142204*a(n-23) -38049*a(n-24) +8201*a(n-25) -1336*a(n-26) +146*a(n-27) -8*a(n-28)
%e A268453 Some solutions for n=7
%e A268453 ..4....4....4....0....2....2....1....0....1....3....3....2....2....4....1....2
%e A268453 ..0....0....0....3....3....0....4....4....1....3....1....1....4....3....0....1
%e A268453 ..1....3....1....2....3....0....4....1....4....1....2....0....4....3....0....1
%e A268453 ..4....0....1....2....3....0....2....2....4....4....2....4....2....3....0....3
%e A268453 ..2....1....1....2....4....4....1....2....0....2....4....3....4....3....2....1
%e A268453 ..2....3....2....1....4....4....4....2....0....1....2....2....0....0....2....3
%e A268453 ..2....2....4....2....0....1....3....0....0....0....4....3....0....4....0....0
%Y A268453 Cf. A268457.
%K A268453 nonn
%O A268453 1,1
%A A268453 _R. H. Hardin_, Feb 04 2016