Numbers n such that sigma(n) / n is prime.

Terms

a(0) =6a(1) =28a(2) =120a(3) =496a(4) =672a(5) =8128a(6) =523776a(7) =33550336a(8) =459818240a(9) =1476304896a(10) =8589869056a(11) =14182439040a(12) =31998395520a(13) =51001180160a(14) =137438691328a(15) =518666803200