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 A038820 #20 Apr 03 2023 10:36:09
%S A038820 4118054813,8007105059,11818439135,15581005657,19308136142,
%T A038820 23007501786,26684074310,30341383527,33981987586,37607912018,
%U A038820 41220703418,44821651132,48411812843,51992079337,55563209929,59125832286
%N A038820 Number of primes less than n*10^11.
%H A038820 Robert G. Wilson v, <a href="/A038820/b038820.txt">Table of n, a(n) for n = 1..10000</a>
%H A038820 Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/primes.html">Tables of values of pi(x) and of pi2(x)</a>
%H A038820 Andrew R. Booker, <a href="https://t5k.org/nthprime/">The Nth Prime Page</a>
%t A038820 Table[ PrimePi[ n*10^11 ], {n, 1, 18}]
%o A038820 (PARI) a(n)=primepi(10^11*n) \\ _Charles R Greathouse IV_, Apr 29 2015
%Y A038820 Cf. A038801, A028505, A038812, A038813, A038814, A038815, A038816, A038817, A038818, A038819, A038821, A080122, A080123, A080124, A080125, A080126, A080127, A080128, A080129.
%K A038820 nonn
%O A038820 1,1
%A A038820 _Jeff Burch_
%E A038820 Edited and extended by _Robert G. Wilson v_, Jan 29 2003