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Search: id:A135060
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| A135060 |
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a(n) = smallest number m for which none of the first n multiples of m has twice as many divisors as m. |
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+0
5
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| 1, 2, 6, 12, 60, 120, 840, 840, 2520, 2520, 27720, 55440, 720720, 720720, 1081080, 2162160
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OFFSET
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1,2
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COMMENT
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a(n) is smallest value m where A129902(m)/m > n.
Conjecture: every number in this sequence is also in A002182. Comment from J. Lowell (jhbubby(AT)mindspring.com), Jun 06 2008: 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 720720.
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EXAMPLE
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60 does not qualify for a(6) because 60 has 12 divisors and 60*6=360 has 12*2=24 divisors
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KEYWORD
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more,nonn,new
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AUTHOR
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J. Lowell (jhbubby(AT)mindspring.com), Feb 11 2008, Jul 08 2008, Jul 14 2008
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EXTENSIONS
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More terms from J. Lowell (jhbubby(AT)mindspring.com), May 13 2009
Corrected inequality in the comment and added a(16) - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 04 2009
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