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 A065685 #16 Dec 15 2024 11:01:18
%S A065685 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
%T A065685 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
%U A065685 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2
%N A065685 Number of primes <= prime(n) which begin with a 6.
%H A065685 Harry J. Smith, <a href="/A065685/b065685.txt">Table of n, a(n) for n = 1..1000</a>
%e A065685 a(17) = 0, a(18) = 1: 61 = A000040(18) is the first prime beginning with 6. a(664579) = 72257 (A000040(664579) = 9999991 is the largest prime < 10^7).
%t A065685 Accumulate@ Array[Boole[First@ IntegerDigits@ Prime@ # == 6] &, 105] (* _Michael De Vlieger_, Jun 14 2018 *)
%o A065685 (PARI) lista(n) = { my(a=[p\10^logint(p,10)==6 | p<-primes(n)]); for(i=2, #a, a[i]+=a[i-1]); a} \\ _Harry J. Smith_, Oct 26 2009
%Y A065685 Cf. A000040, A045712, A065680.
%K A065685 base,nonn
%O A065685 1,19
%A A065685 _Reinhard Zumkeller_, Nov 13 2001