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Search: id:A138009
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| A138009 |
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a(n) = number of positive integers k, k <= n, where d(k) >= d(n); d(n) = number of positive divisors of n. |
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+0
3
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| 1, 1, 2, 1, 4, 1, 6, 2, 4, 3, 10, 1, 12, 5, 6, 2, 16, 2, 18, 3, 10, 11, 22, 1, 15, 13, 14, 5, 28, 2, 30, 7, 18, 19, 20, 1, 36, 22, 23, 4, 40, 5, 42, 11, 12, 28, 46, 1, 33, 14, 31, 15, 52, 7, 34, 8, 36, 37, 58, 1, 60, 39, 19, 10, 42, 10, 66, 22, 45, 11, 70, 2, 72, 48, 25, 26, 51, 13, 78, 4
(list; graph; listen)
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OFFSET
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1,3
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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9 has 3 positive divisors. Among the first 9 positive integers, there are four that have more than or equal the number of divisors than 9 has: 4, with 3 divisors; 6, with 4 divisors; 8, with 4 divisors; and 9, with 3 divisors. So a(9) = 4.
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MATHEMATICA
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Table[Length[Select[Range[n], Length[Divisors[ # ]]>=Length[Divisors[n]]&]], {n, 1, 100}] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Feb 29 2008
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CROSSREFS
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Cf. A079788, A067004.
Sequence in context: A074643 A060794 A074919 this_sequence A131755 A118275 A146938
Adjacent sequences: A138006 A138007 A138008 this_sequence A138010 A138011 A138012
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Feb 27 2008
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Feb 29 2008
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