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 A183721 1/12 the number of (n+1) X 2 0..5 arrays with every 2 X 2 subblock strictly increasing clockwise or counterclockwise with one decrease, and at least two adjacent blocks having the same increasing direction. 1

%I

%S 0,1,12,87,537,3070,16731,88331,455804,2311983,11571209,57295330,

%T 281223411,1370286715,6635743136,31964799247,153273890393,

%U 732031932806,3483896304443,16529018119643,78202676604548,369073777749215

%N 1/12 the number of (n+1) X 2 0..5 arrays with every 2 X 2 subblock strictly increasing clockwise or counterclockwise with one decrease, and at least two adjacent blocks having the same increasing direction.

%C Column 1 of A183729.

%H R. H. Hardin, <a href="/A183721/b183721.txt">Table of n, a(n) for n = 1..200</a>

%F Empirical: a(n) = 8*a(n-1) - 11*a(n-2) - 23*a(n-3) + 6*a(n-4) + 7*a(n-5) - 2*a(n-6).

%F Empirical g.f.: x^2*(1 + 2*x - x^2)^2 / ((1 + x)*(1 - 5*x + 2*x^2)*(1 - 4*x - 2*x^2 + x^3)). - _Colin Barker_, Apr 04 2018

%e All solutions with the first block increasing clockwise for 3 X 2:

%e ..3..4....1..2....4..5....2..3....5..0....0..1

%e ..2..5....0..3....3..0....1..4....4..1....5..2

%e ..1..0....5..4....2..1....0..5....3..2....4..3

%e ...

%e ...R.......R.......R.......R.......R.......R...

%e ...R.......R.......R.......R.......R.......R...

%Y Cf. A183729.

%K nonn

%O 1,3

%A _R. H. Hardin_, Jan 06 2011

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Last modified December 7 08:24 EST 2022. Contains 358649 sequences. (Running on oeis4.)