Numbers k such that 4*10^k - 21 is prime.

Terms

a(0) =1a(1) =2a(2) =4a(3) =5a(4) =7a(5) =9a(6) =10a(7) =17a(8) =21a(9) =41a(10) =51a(11) =59a(12) =61a(13) =77a(14) =79a(15) =83a(16) =97a(17) =108a(18) =427a(19) =615a(20) =869a(21) =900a(22) =966a(23) =3150a(24) =3239a(25) =3932a(26) =5218a(27) =11941a(28) =30558a(29) =44697