Primes p such that sigma(2p-1) = 3*(p-1).

A247788

Primes p such that sigma(2p-1) = 3*(p-1).

Terms

    a(0) =3a(1) =17a(2) =131a(3) =193a(4) =449a(5) =13469a(6) =23297a(7) =581150417

External references