Numbers k such that usigma(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) =257a(14) =512a(15) =514a(16) =544a(17) =640a(18) =680a(19) =768a(20) =816a(21) =960a(22) =1020a(23) =65537a(24) =131072a(25) =131074a(26) =131584a(27) =139264a(28) =139808a(29) =163840