Number of primes less than 10n.

Terms

a(0) =4a(1) =8a(2) =10a(3) =12a(4) =15a(5) =17a(6) =19a(7) =22a(8) =24a(9) =25a(10) =29a(11) =30a(12) =31a(13) =34a(14) =35a(15) =37a(16) =39a(17) =41a(18) =42a(19) =46a(20) =46a(21) =47a(22) =50a(23) =52a(24) =53a(25) =55a(26) =57a(27) =59a(28) =61a(29) =62