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Search: id:A060841
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| A060841 |
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1/det(M) where M is the n X n matrix with M[i,j]= 1/lcm(i,j). |
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+0
1
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| 1, 4, 18, 144, 900, 16200, 132300, 2116800, 28576800, 714420000, 8644482000, 311201352000, 4382752374000, 143169910884000, 4026653743612500, 128852919795600000, 2327405863808025000, 125679916645633350000
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The value is not always an integer! For example, a(35) = 5029296746186844716050163189085401314000634765625/2 . [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 13 2009]
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FORMULA
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a(n) = (n!)^2 / (phi(1)*phi(2)*...*phi(n)) = (n!)^2 / A001088(n)
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EXAMPLE
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a(2) = 4 because the matrix M is: [1,1/2; 1/2,1/2] and det(M) = 1/4
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CROSSREFS
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A001088, A000010, A060238.
Sequence in context: A065857 A156445 A143992 this_sequence A059837 A054759 A007153
Adjacent sequences: A060838 A060839 A060840 this_sequence A060842 A060843 A060844
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KEYWORD
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nonn,easy
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AUTHOR
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Noam Katz (noamkj(AT)hotmail.com), May 02 2001
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EXTENSIONS
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More terms from Reiner Martin (reinermartin(AT)hotmail.com), May 17 2001
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