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A063785
Numbers n such that sigma(n) = 2n + omega(n), where omega(n) is the number of distinct prime divisors of n.
0
20, 104, 464, 1952, 4030, 5830, 130304, 522752, 1848964, 8382464, 134193152
OFFSET
1,1
COMMENTS
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
PROG
(PARI) for(n=1, 10^8, if(sigma(n)==2*n+omega(n), print(n)))
CROSSREFS
Cf. A045768.
Sequence in context: A189950 A045768 A088831 * A181703 A334419 A187756
KEYWORD
nonn,more
AUTHOR
Jason Earls, Aug 17 2001
STATUS
approved