Numbers k such that the number of primes <= k is phi(phi(k)).

Terms

a(0) =2a(1) =37a(2) =55a(3) =91a(4) =95a(5) =136a(6) =178a(7) =226a(8) =507a(9) =723a(10) =1166a(11) =1168a(12) =1284a(13) =1323a(14) =2658a(15) =3082a(16) =7564a(17) =8166a(18) =11578a(19) =12014a(20) =12018a(21) =12026a(22) =15340a(23) =40220a(24) =50544a(25) =55490a(26) =56810a(27) =69732a(28) =89210a(29) =100114