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A205991 Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to two, and every 2 X 2 determinant nonzero. 1

%I #9 Jun 13 2018 05:47:17

%S 26,92,330,1184,4250,15252,54738,196448,705026,2530252,9080754,

%T 32589688,116960298,419755820,1506450938,5406463248,19403117738,

%U 69635353188,249912538754,896904721104,3218878423314,11552150479772,41459217515106

%N Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to two, and every 2 X 2 determinant nonzero.

%C Column 1 of A205998.

%H R. H. Hardin, <a href="/A205991/b205991.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 2*a(n-1) + 5*a(n-2) + 3*a(n-3) - 2*a(n-4) + a(n-5).

%F Empirical g.f.: 2*x*(13 + 20*x + 8*x^2 - 7*x^3 + 4*x^4) / (1 - 2*x - 5*x^2 - 3*x^3 + 2*x^4 - x^5). - _Colin Barker_, Jun 13 2018

%e Some solutions for n=4:

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

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

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

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

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

%Y Cf. A205998.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 02 2012

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Last modified February 23 14:24 EST 2024. Contains 370283 sequences. (Running on oeis4.)