a(n) = prime(prime(A028815(n) - 1) - 1) - 1.

Terms

a(0) =1a(1) =2a(2) =6a(3) =28a(4) =52a(5) =112a(6) =172a(7) =270a(8) =316a(9) =420a(10) =592a(11) =700a(12) =910a(13) =1060a(14) =1150a(15) =1290a(16) =1510a(17) =1782a(18) =1830a(19) =2212a(20) =2376a(21) =2472a(22) =2740a(23) =2998a(24) =3256a(25) =3630a(26) =3930a(27) =4078a(28) =4270a(29) =4390