Semiprimes s such that s-/+4 are primes.

Terms

a(0) =9a(1) =15a(2) =33a(3) =57a(4) =93a(5) =177a(6) =237a(7) =267a(8) =393a(9) =453a(10) =573a(11) =597a(12) =687a(13) =723a(14) =933a(15) =1167a(16) =1227a(17) =1293a(18) =1527a(19) =1563a(20) =1623a(21) =1983a(22) =2157a(23) =2217a(24) =2463a(25) =2913a(26) =3327a(27) =3453a(28) =3543a(29) =4353