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A136609
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(1/(n!)^2) * number of ways to arrange the consecutive numbers 1...n^2 in an n X n matrix with determinant = 0.
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4
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OFFSET
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1,3
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COMMENTS
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The computation of a(5) seems to be currently (Jan 2008) out of reach (compare with A088021(5)).
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LINKS
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EXAMPLE
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a(1)=0 because det((1))/=0, a(2)=0, because the only possible determinants of a matrix with elements {1,2,3,4} are +-2, +-5 and +-10.
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CROSSREFS
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KEYWORD
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hard,more,nonn
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AUTHOR
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STATUS
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approved
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