Numbers k such that 10*k-1, 10*k-3, 10*k-7 and 10*k-9 are all prime.

Terms

a(0) =2a(1) =11a(2) =20a(3) =83a(4) =149a(5) =188a(6) =209a(7) =326a(8) =347a(9) =566a(10) =944a(11) =1301a(12) =1565a(13) =1574a(14) =1607a(15) =1805a(16) =1892a(17) =1943a(18) =2102a(19) =2228a(20) =2531a(21) =3173a(22) =3485a(23) =4379a(24) =5135a(25) =5534a(26) =6299a(27) =6722a(28) =6950a(29) =7223