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Search: id:A066423
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| A066423 |
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Product of proper divisors of the n-th composite number does not equal the n-th composite number. |
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+0
3
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| 4, 9, 12, 16, 18, 20, 24, 25, 28, 30, 32, 36, 40, 42, 44, 45, 48, 49, 50, 52, 54, 56, 60, 63, 64, 66, 68, 70, 72, 75, 76, 78, 80, 81, 84, 88, 90, 92, 96, 98, 99, 100, 102, 104, 105, 108, 110, 112, 114, 116, 117, 120, 121, 124, 126, 128, 130, 132
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A084115(a(n))>1; complement of A084116. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 12 2003
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EXAMPLE
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The fourth composite number is 9. Its proper or aliquot divisors are 1 and 3. The product of 1 and 3 equals 3 which is not equal to 9. Therefore 9 is in the sequence.
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MATHEMATICA
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Composite[n_] := FixedPoint[n + PrimePi[ # ] + 1 &, n + PrimePi[n] + 1]; Do[m = Composite[n]; If[ Apply[ Times, Drop[ Divisors[m], -1]] != m, Print[m]], {n, 1, 100} ]
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CROSSREFS
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Cf. A048741.
Sequence in context: A161544 A010386 A094120 this_sequence A072498 A162643 A072587
Adjacent sequences: A066420 A066421 A066422 this_sequence A066424 A066425 A066426
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 26 2001
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