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 A065311 #18 Nov 06 2017 02:48:12
%S A065311 3,5,13,17,29,31,43,67,71,97,107,109,131,157,181,191,223,233,239,269,
%T A065311 281,313,359,379,383,401,409,431,503,523,569,571,619,631,659,691,719,
%U A065311 751,787,797,857,859,881,883,971,1039,1061,1063,1091,1117,1123,1201
%N A065311 Primes which occur exactly twice in the sequence of a(n) = prime(n) - prime(n - pi(n)) = A065308(n).
%C A065311 In A065308, each odd prime seems to appear once or twice.
%H A065311 Harry J. Smith, <a href="/A065311/b065311.txt">Table of n, a(n) for n = 1..1000</a>
%t A065311 Most@ Select[Tally@ Array[Prime[# - PrimePi@ #] &, 300], Last@ # == 2 &][[All, 1]] (* _Michael De Vlieger_, Nov 03 2017 *)
%o A065311 (PARI) { n=0; p=1; f=2; m=1; for (i=1, 10^9, a=0; p=nextprime(p + 1); while (p==f, a++; m++; f=prime(m - primepi(m))); if (a==2, write("b065311.txt", n++, " ", p); if (n==1000, return)) ) } \\ _Harry J. Smith_, Oct 16 2009
%Y A065311 Cf. A000040, A000720, A054546, A065308, A065309, A065310, A065311.
%K A065311 nonn
%O A065311 1,1
%A A065311 _Labos Elemer_, Oct 29 2001