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A246474 Number of length n+3 0..3 arrays with no pair in any consecutive four terms totalling exactly 3.

%I A246474 #7 Nov 06 2018 04:12:30
%S A246474 60,132,292,644,1420,3132,6908,15236,33604,74116,163468,360540,795196,
%T A246474 1753860,3868260,8531716,18817292,41502844,91537404,201892100,
%U A246474 445287044,982111492,2166115084,4777517212,10537145916,23240406916,51258331044
%N A246474 Number of length n+3 0..3 arrays with no pair in any consecutive four terms totalling exactly 3.
%H A246474 R. H. Hardin, <a href="/A246474/b246474.txt">Table of n, a(n) for n = 1..210</a>
%F A246474 Empirical: a(n) = 2*a(n-1) + a(n-3).
%F A246474 Empirical g.f.: 4*x*(15 + 3*x + 7*x^2) / (1 - 2*x - x^3). - _Colin Barker_, Nov 06 2018
%e A246474 Some solutions for n=6:
%e A246474 ..2....3....2....1....0....2....1....0....0....2....1....3....2....0....2....1
%e A246474 ..0....3....2....1....2....2....3....0....2....0....1....3....3....0....2....3
%e A246474 ..0....2....2....0....0....2....1....0....2....2....1....3....2....0....3....1
%e A246474 ..2....2....2....1....0....2....1....0....2....2....0....3....3....1....3....3
%e A246474 ..0....2....3....1....0....2....1....0....2....2....0....1....2....1....2....3
%e A246474 ..0....2....3....0....0....2....1....0....3....0....0....1....2....1....3....3
%e A246474 ..0....2....3....0....0....3....1....2....3....0....1....1....2....3....3....3
%e A246474 ..0....0....3....1....0....2....3....0....3....0....0....3....2....1....2....1
%e A246474 ..1....0....2....0....0....3....1....2....2....0....1....1....0....3....2....3
%Y A246474 Column 3 of A246479.
%K A246474 nonn
%O A246474 1,1
%A A246474 _R. H. Hardin_, Aug 27 2014