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 A231592 #14 Jun 16 2019 13:20:37
%S A231592 1,9,75,677,6229,58770,564650,5472472,53396224,523382007,5148387363,
%T A231592 50778098799,501864775685,4968288427006
%N A231592 Total number of 3's digits in primes less than 10^n.
%e A231592 a(2)=9, since there are 9 3's in primes less than 100. Namely: 3, 13, 23, 31, 37, 43, 53, 73, 83.
%t A231592 Table[Count[IntegerDigits[Prime[Range[PrimePi[10^n - 1]]]], 3, 2], {n, 7}] (* _Robert Price_, Jun 16 2019 *)
%Y A231592 Cf. A231411, A231590-A231598, A119290, A119291-A119300.
%K A231592 nonn,base,more
%O A231592 1,2
%A A231592 _Robert Price_, Nov 11 2013
%E A231592 a(14) from _Giovanni Resta_, Jul 20 2015