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 A231598 #14 Jun 16 2019 14:56:51
%S A231598 0,6,67,646,6130,58145,558956,5432190,53071838,520787464,5127052380,
%T A231598 50599825547,500350977737,4955299345646
%N A231598 Total number of 9's digits in primes less than 10^n.
%e A231598 a(2)=6, since there are 6 9's in primes less than 100. Namely: 19, 29, 59, 79, 89, 97.
%t A231598 Table[Count[IntegerDigits[Prime[Range[PrimePi[10^n - 1]]]], 9, 2], {n, 7}] (* _Robert Price_, Jun 16 2019 *)
%Y A231598 Cf. A231411, A231590-A231598, A119290, A119291-A119300.
%K A231598 nonn,base,more
%O A231598 1,2
%A A231598 _Robert Price_, Nov 11 2013
%E A231598 a(14) from _Giovanni Resta_, Jul 20 2015