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

Terms

a(0) =2a(1) =3a(2) =12a(3) =15a(4) =35a(5) =56a(6) =78a(7) =140a(8) =190a(9) =357a(10) =630a(11) =812a(12) =910a(13) =1045a(14) =1672a(15) =2214a(16) =2580a(17) =3339a(18) =4180a(19) =4522a(20) =4674a(21) =5049a(22) =5278a(23) =5544a(24) =8008a(25) =10659a(26) =11160a(27) =12441a(28) =16065a(29) =16120