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Search: id:A141717
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| A141717 |
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Numbers n such that the set of prime factors of phi(n) is a proper subset of the set of prime factors of n and the set of prime factors of n is a proper subset of the set of prime factors of sigma(n). |
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1
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| 24, 40, 96, 234, 360, 384, 540, 600, 640, 936, 1536, 1920, 2016, 2160, 2176, 3000, 3240, 3402, 3744, 4320, 4680, 5760, 6048, 6144, 6318, 6528, 6552, 8640, 9600, 9720, 10240, 10880, 11172, 11466, 13608, 14976, 15000, 17280, 18144, 19584
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Prime Puzzles & Problems Connections, Puzzle 451, Prime factors of n, [nonascii characters here]
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EXAMPLE
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The set of prime factors of phi(24)is {2}, the set of prime factors of 24 is {2,3} and the set of prime factors of sigma(24) is {2,3,5} so 24 is in the sequence.
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CROSSREFS
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Sequence in context: A039296 A043899 A026040 this_sequence A007372 A062910 A098900
Adjacent sequences: A141714 A141715 A141716 this_sequence A141718 A141719 A141720
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KEYWORD
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easy,nonn
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AUTHOR
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Farideh Firoozbakht (mymontain(AT)yahoo.com), Aug 22 2008
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