Numbers k such that sigma(phi(k)) is a prime.

Terms

a(0) =3a(1) =4a(2) =5a(3) =6a(4) =8a(5) =10a(6) =12a(7) =17a(8) =32a(9) =34a(10) =40a(11) =48a(12) =60a(13) =85a(14) =128a(15) =136a(16) =160a(17) =170a(18) =192a(19) =204a(20) =240a(21) =4369a(22) =8192a(23) =8224a(24) =8704a(25) =8738a(26) =10240a(27) =10280a(28) =10880a(29) =12288