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A048107
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Number of unitary divisors of n (A034444) > number of non-unitary divisors of n (A048105).
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4
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1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 28, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 55, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 82, 83, 84, 85, 86
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The sequence includes squarefree numbers (A005117) and more, like the 420, etc.
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FORMULA
| Numbers for which 2^(r(n)+1)>d(n) holds, where r() =A001221, d() = A000005
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EXAMPLE
| n=420=2*2*3*5*7, 4 distinct prime factors, 24 divisors of which 16 are unitary and 8 are not; ud[ n ]>nud[ n ] and 2^(4+1)=32 is larger than d, the number of divisors.
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CROSSREFS
| A000005, A001221, A034444, A005117.
Sequence in context: A023802 A007915 A004709 * A078129 A188437 A003796
Adjacent sequences: A048104 A048105 A048106 * A048108 A048109 A048110
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu)
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