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A302681
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.
1
4, 4, 8, 12, 18, 40, 94, 184, 358, 760, 1594, 3220, 6574, 13636, 28078, 57460, 118090, 243232, 499846, 1026496, 2110462, 4339696, 8918722, 18329596, 37680070, 77455324, 159200278, 327229276, 672635458, 1382602264, 2841890926, 5841485128
OFFSET
1,1
COMMENTS
Row 3 of A302680.
LINKS
FORMULA
Empirical: a(n) = a(n-1) +3*a(n-3) +3*a(n-4) for n>7
EXAMPLE
Some solutions for n=5
..0..1..0..1..0. .0..1..1..1..0. .0..1..0..1..0. .0..0..0..1..0
..0..1..0..1..0. .0..1..0..1..0. .0..1..1..1..0. .0..1..0..1..0
..0..1..0..0..0. .0..1..0..1..0. .0..1..0..1..0. .0..1..1..1..0
CROSSREFS
Cf. A302680.
Sequence in context: A003829 A194697 A194696 * A002368 A299474 A022087
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 11 2018
STATUS
approved