Initial prime in set of 4 consecutive primes with common difference 6.

Terms

a(0) =251a(1) =1741a(2) =3301a(3) =5101a(4) =5381a(5) =6311a(6) =6361a(7) =12641a(8) =13451a(9) =14741a(10) =15791a(11) =15901a(12) =17471a(13) =18211a(14) =19471a(15) =23321a(16) =26171a(17) =30091a(18) =30631a(19) =53611a(20) =56081a(21) =62201a(22) =63691a(23) =71341a(24) =75521a(25) =77551a(26) =78791a(27) =80911a(28) =82781a(29) =83431