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 A065682 #16 Dec 15 2024 11:01:30
%S A065682 0,1,1,1,1,1,1,1,1,1,2,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
%T A065682 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,4,5,6,7,8,9,
%U A065682 10,11,12,13,14,15,16,17,18,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19
%N A065682 Number of primes <= prime(n) which begin with a 3.
%H A065682 Harry J. Smith, <a href="/A065682/b065682.txt">Table of n, a(n) for n = 1..1000</a>
%e A065682 a(1) = 0, a(2) = 1. a(664579) = 75290 (A000040(664579) = 9999991 is the largest prime < 10^7).
%t A065682 Accumulate@ Array[Boole[First@ IntegerDigits@ Prime@ # == 3] &, 87] (* _Michael De Vlieger_, Jun 14 2018 *)
%o A065682 (PARI) lista(n) = { my(a=[p\10^logint(p,10)==3 | p<-primes(n)]); for(i=2, #a, a[i]+=a[i-1]); a} \\ _Harry J. Smith_, Oct 26 2009
%Y A065682 Cf. A000040, A045709, A065680.
%K A065682 base,nonn
%O A065682 1,11
%A A065682 _Reinhard Zumkeller_, Nov 13 2001