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 A240679 #12 Jan 24 2019 15:21:42
%S A240679 2,3,5,17,23,37,59,67,73,97,101,127,149,157,193,197,211,223,229,233,
%T A240679 239,241,269,283,331,337,349,353,373,379,401,433,439,463,467,479,487,
%U A240679 499,571,607,613,619,631,673,691,701,733,757,769,811,853,859,937,941
%N A240679 Primes p such that p*10+k is prime for exactly two values of the digit k.
%H A240679 Colin Barker, <a href="/A240679/b240679.txt">Table of n, a(n) for n = 1..1000</a>
%e A240679 2 is in the sequence because 23 and 29 are prime, but 21 and 27 are not prime.
%t A240679 Select[Prime[Range[200]],Count[Table[10 #+k,{k,{1,3,7,9}}],_?PrimeQ] == 2&] (* _Harvey P. Dale_, Jan 24 2019 *)
%o A240679 (PARI) forprime(p=2, 1500, t=0; forstep(k=1, 9, 2, if(isprime(p*10+k), t++)); if(t==2, print1(p, ", ")))
%Y A240679 Cf. A067267, A119289, A240678, A240680, A240689.
%K A240679 nonn,base
%O A240679 1,1
%A A240679 _Colin Barker_, Apr 10 2014