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Number of nX3 0..1 arrays with new values 0..1 introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors.
2

%I #26 Apr 06 2016 12:51:09

%S 4,28,196,1372,9604,67228,470596,3294172,23059204,161414428,

%T 1129900996,7909306972,55365148804,387556041628,2712892291396,

%U 18990246039772,132931722278404,930522055948828,6513654391641796,45595580741492572

%N Number of nX3 0..1 arrays with new values 0..1 introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors.

%C Column 3 of A208709.

%H R. H. Hardin, <a href="/A208704/b208704.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 7*a(n-1).

%F Empirical: a(n) = (A198480(n)+1)*2 = (A024075(n)+1)*4. [_Martin Ettl_, Nov 09 2012; revised Nov 13 2012]

%e Some solutions for n=4

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

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

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

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

%Y Cf. A270471.

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 01 2012