1,1

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

Table of n, a(n) for n=1..11.

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

Cf. A045768.

Sequence in context: A189950 A045768 A088831 * A181703 A187756 A248087

Adjacent sequences: A063782 A063783 A063784 * A063786 A063787 A063788

nonn

Jason Earls, Aug 17 2001

approved