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 A231590 #15 Jun 16 2019 14:00:22
%S A231590 0,9,78,681,6353,59634,570157,5510645,53680317,525651276,5166809159,
%T A231590 50931212973,503152799893,4979293536415
%N A231590 Total number of 1's digits in primes less than 10^n.
%e A231590 a(2)=9, since there are 9 1's in primes less than 100. Namely: 11, 13, 17, 19, 31, 41, 61, 71. Note that 11 counts for two.
%t A231590 Table[Count[IntegerDigits[Prime[Range[PrimePi[10^n - 1]]]], 1, 2], {n, 7}] (* _Robert Price_, Jun 16 2019 *)
%Y A231590 Cf. A231411, A231590-A231598, A119290, A119291-A119300.
%K A231590 nonn,base,more
%O A231590 1,2
%A A231590 _Robert Price_, Nov 11 2013
%E A231590 a(14) from _Giovanni Resta_, Jul 20 2015