A063785 Numbers n such that sigma(n) = 2n + omega(n), where omega(n) is the number of distinct prime divisors of n.

20, 104, 464, 1952, 4030, 5830, 130304, 522752, 1848964, 8382464, 134193152

Offset: 1

Author

Jason Earls, Aug 17 2001

Keywords

• nonn
• more

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

Crossrefs

Cf. A045768.

Programs

PARI

for(n=1,10^8, if(sigma(n)==2*n+omega(n),print(n)))