Number of primes < 10^n.

Terms

a(0) =0a(1) =4a(2) =25a(3) =168a(4) =1229a(5) =9592a(6) =78498a(7) =664579a(8) =5761455a(9) =50847534a(10) =455052511a(11) =4118054813a(12) =37607912018a(13) =346065536839