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 A306890 #17 Apr 11 2019 21:33:09
%S A306890 1,2,3,4,4,5,6,6,8,9,10,12,12,13,14,16,17,17,18,19,21,22,23,23,24,24,
%T A306890 25,26,26,27,29,30,32,33,33,34,36,37,38,40,41,41,41,42,43,43,44,47,50,
%U A306890 52,55,57,58,60,63,65,66,68,71,72,74,76,78,79
%N A306890 a(n) is the number of prime digits used in writing out all primes up to and including the n-th prime.
%e A306890 We have a(10) = 9 since all primes up to the 10th (2, 3, 5, 7, 11, 13, 17, 19, 23, 29) use the 9 prime digits 2, 3, 5, 7, 3, 7, 2, 3, 2.
%t A306890 With[{s = IntegerDigits[Prime@ Range@ 64]}, Array[Count[Flatten[s[[1 ;; #]] ], _?PrimeQ] &, Length@ s]] (* _Michael De Vlieger_, Mar 27 2019 *)
%o A306890 (PARI) a(n) = sum(k=1, prime(n), if (isprime(k), #select(x->isprime(x), digits(k)))); \\ _Michel Marcus_, Mar 23 2019
%Y A306890 Partial sums of A109066. Cf. A068670.
%K A306890 nonn,base
%O A306890 1,2
%A A306890 _Lekraj Beedassy_, Mar 15 2019