Numbers k such that 6k+1, 12k+1, 18k+1 and 36k+1 are all primes.

Terms

a(0) =1a(1) =45a(2) =56a(3) =121a(4) =206a(5) =255a(6) =380a(7) =506a(8) =511a(9) =710a(10) =871a(11) =1025a(12) =1421a(13) =1515a(14) =1696a(15) =2191a(16) =2571a(17) =2656a(18) =2681a(19) =3341a(20) =3566a(21) =3741a(22) =3796a(23) =3916a(24) =3976a(25) =4235a(26) =4340a(27) =4426a(28) =5645a(29) =5875