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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 nXn matrix with determinant = 0.
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1
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OFFSET
| 1,3
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COMMENTS
| The computation of a(5) seems to be currently (Jan 2008) out of reach (compare with A088021(5)).
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EXAMPLE
| 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
| Cf. a(3)=A088215(0), a(4)=A136608(0), A046747 [{0, 1}-matrices with determinant 0].
Sequence in context: A033521 A060716 A116255 * A116246 A128670 A033397
Adjacent sequences: A136606 A136607 A136608 * A136610 A136611 A136612
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KEYWORD
| hard,more,nonn
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AUTHOR
| Hugo Pfoertner (hugo(AT)pfoertner.org), Jan 21 2008
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