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Search: id:A063785
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| A063785 |
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Numbers n such that sigma(n) = 2n + omega(n), where omega(n) is the number of distinct prime divisors of n. |
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+0
1
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| 20, 104, 464, 1952, 4030, 5830, 130304, 522752, 1848964, 8382464, 134193152
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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It is easily proved that if 2^m-3 is prime then 2^(m-1)*(2^m-3) is in the sequence. - Farideh Firoozbakht (mymontain(AT)yahoo.com), Feb 12 2008
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PROGRAM
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(PARI) for(n=1, 10^8, if(sigma(n)==2*n+omega(n), print(n)))
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CROSSREFS
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Cf. A045768.
Sequence in context: A071334 A045768 A088831 this_sequence A135174 A109854 A008383
Adjacent sequences: A063782 A063783 A063784 this_sequence A063786 A063787 A063788
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KEYWORD
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nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Aug 17 2001
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