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 A240680 #10 Apr 07 2023 12:01:08
%S A240680 7,13,31,43,61,103,109,199,271,367,409,421,523,541,547,787,823,829,
%T A240680 883,1009,1033,1117,1237,1291,1669,1999,2131,2161,2203,2269,2437,2503,
%U A240680 2593,2671,2857,3049,3253,3271,3361,3559,3583,3769,3823,4003,4201,4339,4357
%N A240680 Primes p such that p*10+k is prime for exactly three values of the digit k.
%H A240680 Bruno Berselli, <a href="/A240680/b240680.txt">Table of n, a(n) for n = 1..1000</a>
%e A240680 7 is in the sequence because 71, 73 and 79 are prime, but 77 is not prime.
%t A240680 Select[Prime[Range[600]],Total[Boole[PrimeQ[10#+{1,3,7,9}]]]==3&] (* _Harvey P. Dale_, Apr 07 2023 *)
%o A240680 (PARI) forprime(p=2, 10000, t=0; forstep(k=1, 9, 2, if(isprime(p*10+k), t++)); if(t==3, print1(p, ", ")))
%o A240680 (Magma) [p: p in PrimesUpTo(10^4) | {k: k in [1,3,7,9] | IsPrime(p*10+k)} in Subsets({1,3,7,9},3)]; // _Bruno Berselli_, Apr 10 2014
%Y A240680 Cf. A067267, A119289, A240678, A240679, A240689.
%K A240680 nonn,base
%O A240680 1,1
%A A240680 _Colin Barker_, Apr 10 2014