Numbers n such that 4*10^n + 1 is prime.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =13a(5) =229a(6) =242a(7) =309a(8) =957a(9) =1473a(10) =1494a(11) =3182a(12) =3727a(13) =4177a(14) =23210a(15) =25719a(16) =32835a(17) =36990a(18) =103958a(19) =789955a(20) =1038890