This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A210518 #40 Sep 06 2024 08:06:15
%S A210518 0,0,2,3,4,7,11,16,25,40,65,102,168,275,446,739,1229,2039,3401,5703,
%T A210518 9592,16144,27293,46243,78498,133551,227647,388683,664579,1138288,
%U A210518 1951957,3351550,5761455,9915892,17082666,29458442,50847534,87842213,151876932,262795354
%N A210518 Number of primes up to 10^(n/4).
%H A210518 Amiram Eldar, <a href="/A210518/b210518.txt">Table of n, a(n) for n = 0..80</a> (calculated using Kim Walisch's primecount)
%H A210518 Kim Walisch, <a href="https://github.com/kimwalisch/primecount">Fast C++ prime counting function implementation (primecount)</a>.
%F A210518 a(n) = primepi(10^(n/4)) = A000720(A018072(n)).
%e A210518 a(1) = 0 because 10^(1/4) = 1.77828... and there are no primes less than that.
%e A210518 a(2) = 2 because sqrt(10) = 3.16228... and there are 2 primes below that.
%e A210518 a(3) = 3 because 10^(3/4) = 5.62341... and there are 3 primes below that.
%t A210518 Table[PrimePi[10^(n/4)], {n, 0, 39}] (* _Alonso del Arte_, Jan 26 2013 *)
%Y A210518 Cf. A000720, A006880, A018072.
%K A210518 nonn,hard
%O A210518 0,3
%A A210518 _Vladimir Pletser_, Jan 26 2013