Mersenne numbers with at most 2 prime factors.

A006515

Mersenne numbers with at most 2 prime factors.

Terms

    a(0) =3a(1) =7a(2) =31a(3) =127a(4) =2047a(5) =8191a(6) =131071a(7) =524287a(8) =8388607a(9) =2147483647a(10) =137438953471

External references