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A215866
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Number of permutations of 0..floor((n*6-2)/2) on odd squares of an n X 6 array such that each row, column, diagonal and (downwards) antidiagonal of odd squares is increasing.
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2
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1, 5, 12, 78, 189, 1233, 2988, 19494, 47241, 308205, 746892, 4872798, 11808549, 77040153, 186696108, 1218024054, 2951712081, 19257264405, 46667304972, 304462158318, 737821743309, 4813622739873, 11665145978028, 76104577363014
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 16*a(n-2) -3*a(n-4).
Empirical: g.f.: -x*(x-1)*(2*x^2+6*x+1) / ( 1-16*x^2+3*x^4 ). - R. J. Mathar, Nov 27 2015
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EXAMPLE
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Some solutions for n=4:
..x..0..x..1..x..4....x..0..x..2..x..3....x..0..x..2..x..3....x..0..x..2..x..3
..2..x..3..x..5..x....1..x..4..x..6..x....1..x..4..x..7..x....1..x..4..x..6..x
..x..6..x..8..x.10....x..5..x..8..x..9....x..5..x..8..x..9....x..5..x..7..x..8
..7..x..9..x.11..x....7..x.10..x.11..x....6..x.10..x.11..x....9..x.10..x.11..x
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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