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A135060
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a(n) is the smallest number m for which none of the first n multiples of m has twice as many divisors as m.
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5
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1, 2, 6, 12, 60, 120, 840, 840, 2520, 2520, 27720, 55440, 720720, 720720, 1081080, 2162160, 36756720, 36756720, 698377680, 698377680, 698377680, 698377680, 16062686640, 48188059920, 160626866400, 160626866400, 160626866400
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OFFSET
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1,2
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COMMENTS
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a(n) is smallest integer m such that A129902(m)/m > n.
The conjecture that every term is a multiple of the preceding term is disproved at n = 15; a(15) = 1081080, which is not a multiple of a(14) = 720720. - J. Lowell, Jun 06 2008
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LINKS
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EXAMPLE
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60 is not a(6) because 60 has 12 divisors and 60*6=360 has 12*2=24 divisors.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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J. Lowell, Feb 11 2008, Jul 08 2008, Jul 14 2008
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EXTENSIONS
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Inequality in the comment corrected and a(16) added by R. J. Mathar, Nov 04 2009
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STATUS
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approved
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