Number of primes <= 10^(n/2).

Terms

a(0) =0a(1) =2a(2) =4a(3) =11a(4) =25a(5) =65a(6) =168a(7) =446a(8) =1229a(9) =3401a(10) =9592a(11) =27293a(12) =78498a(13) =227647a(14) =664579a(15) =1951957a(16) =5761455a(17) =17082666a(18) =50847534a(19) =151876932a(20) =455052511a(21) =1367199811a(22) =4118054813a(23) =12431880460a(24) =37607912018a(25) =113983535775a(26) =346065536839