Perfect powers n such that (n-17)/2 is prime.

Terms

a(0) =27a(1) =243a(2) =343a(3) =19683a(4) =29791a(5) =300763a(6) =421875a(7) =493039a(8) =658503a(9) =759375a(10) =1367631a(11) =2048383a(12) =2685619a(13) =3176523a(14) =4019679a(15) =5000211a(16) =8869743a(17) =9393931a(18) =15069223a(19) =17373979a(20) =19034163a(21) =25672375a(22) =32461759a(23) =43243551a(24) =52734375a(25) =54439939a(26) =63521199a(27) =82312875a(28) =84604519