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%I #4 Apr 11 2018 12:29:13
%S 4,4,8,12,18,40,94,184,358,760,1594,3220,6574,13636,28078,57460,
%T 118090,243232,499846,1026496,2110462,4339696,8918722,18329596,
%U 37680070,77455324,159200278,327229276,672635458,1382602264,2841890926,5841485128
%N Number of 3Xn 0..1 arrays with every element equal to 0, 1, 4 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero.
%C Row 3 of A302680.
%H R. H. Hardin, <a href="/A302681/b302681.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = a(n-1) +3*a(n-3) +3*a(n-4) for n>7
%e Some solutions for n=5
%e ..0..1..0..1..0. .0..1..1..1..0. .0..1..0..1..0. .0..0..0..1..0
%e ..0..1..0..1..0. .0..1..0..1..0. .0..1..1..1..0. .0..1..0..1..0
%e ..0..1..0..0..0. .0..1..0..1..0. .0..1..0..1..0. .0..1..1..1..0
%Y Cf. A302680.
%K nonn
%O 1,1
%A _R. H. Hardin_, Apr 11 2018
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