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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
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20, 104, 464, 1952, 4030, 5830, 130304, 522752, 1848964, 8382464, 134193152
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OFFSET
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1,1
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COMMENTS
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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, Feb 12 2008
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LINKS
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PROG
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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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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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