Semiprime function n -> A001358(n) applied four times to n.

Terms

a(0) =77a(1) =119a(2) =219a(3) =235a(4) =377a(5) =381a(6) =566a(7) =634a(8) =721a(9) =779a(10) =998a(11) =1006a(12) =1126a(13) =1282a(14) =1294a(15) =1563a(16) =1642a(17) =1745a(18) =1853a(19) =1959a(20) =1961a(21) =2209a(22) =2402a(23) =2483a(24) =2554a(25) =2785a(26) =3005a(27) =3149a(28) =3173a(29) =3242