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 A185712 #17 Jul 11 2017 04:51:54
%S A185712 0,0,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,3,
%T A185712 3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
%U A185712 5,5,5,5,6,6,6,6,6,6,6,6,6,6,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,8,8,8,8,8,8,8,8,8,8,9,9,9,9,9,9,9,9
%N A185712 a(n) = number of primes <= n that end in 3.
%C A185712 Partial sums of A185706.
%H A185712 G. C. Greubel, <a href="/A185712/b185712.txt">Table of n, a(n) for n = 1..5000</a>
%H A185712 A. Granville and G. Martin, <a href="http://www.arXiv.org/abs/math.NT/0408319">Prime number races</a>, arXiv:math/0408319 [math.NT], 2004.
%H A185712 A. Granville and G. Martin, <a href="http://www.dms.umontreal.ca/~andrew/PDF/PrimeRace.pdf">Prime number races</a>, Amer. Math. Monthly, 113 (No. 1, 2006), 1-33.
%t A185712 Accumulate[Table[If[PrimeQ[n] && Mod[n, 10] == 3, 1, 0], {n, 50}]] (* _G. C. Greubel_, Jul 10 2017 *)
%Y A185712 Cf. A185705, A185706, A185708, A185709, A185711, A185712, A185714, A185715.
%K A185712 base,nonn
%O A185712 1,13
%A A185712 _N. J. A. Sloane_, Feb 10 2011