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Search: id:A109423
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| A109423 |
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Numbers n such that sigma(n)/bigomega(n) is an integer [sigma(n) =sum of divisors of n; bigomega(n)=number of prime divisors of n, counted with multiplicity]. |
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+0
2
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| 2, 3, 5, 6, 7, 8, 10, 11, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 26, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 50, 51, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 77, 78, 79, 82, 83, 84, 85, 86, 87, 88, 89, 91, 92
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Integers greater than 1 and not in A109424.
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EXAMPLE
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The number 24 is in the sequence because sigma(24)=60 (1+2+3+4+6+8+12+24) and bigomega(24)=4 (2,2,2,3) and so sigma(24)/bigomega(24)=15.
The number 12 is not in the sequence because sigma(12)=28 (1+2+3+4+6+12) and bigomega(12)=3 (2,2,3) and so sigma(12)/bigomega(12)=28/3.
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MAPLE
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with(numtheory): a:=proc(n) if type(sigma(n)/bigomega(n), integer)=true then n else fi end: seq(a(n), n=2..110);
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CROSSREFS
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Cf. A109424.
Sequence in context: A000452 A047587 A028737 this_sequence A028801 A162644 A002035
Adjacent sequences: A109420 A109421 A109422 this_sequence A109424 A109425 A109426
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KEYWORD
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nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 28 2005
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