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 A289867 #18 May 12 2024 11:28:55
%S A289867 67,613,617,619,631,641,643,647,653,659,661,673,683,6101,6113,6131,
%T A289867 6151,6163,6173,6197,6199,6211,6229,6257,6263,6269,6271,6277,6311,
%U A289867 6317,6337,6353,6359,6367,6373,6379,6389,6397,6421,6449,6491,6521,6547,6563
%N A289867 Primes obtained from other primes by prefixing a 6.
%H A289867 Robert Israel, <a href="/A289867/b289867.txt">Table of n, a(n) for n = 1..10000</a>
%e A289867 613 is a term because it is a prime obtained by prefixing a 6 to the prime 13.
%e A289867 6101 is a term because it is a prime obtained by prefixing a 6 to the prime 101.
%p A289867 p:= 0: A:= NULL:
%p A289867 while p < 1000 do
%p A289867 p:= nextprime(p);
%p A289867 q:= 10^(ilog10(p)+1)*6+p;
%p A289867 if isprime(q) then A:= A, q; fi
%p A289867 od:
%p A289867 A; # _Robert Israel_, Jul 17 2017
%t A289867 Select[Table[FromDigits[Join[IntegerDigits[6], IntegerDigits[Prime[n]]]], {n, 110}], PrimeQ]
%t A289867 Select[6*10^IntegerLength[#]+#&/@Prime[Range[150]],PrimeQ] (* _Harvey P. Dale_, Apr 03 2022 *)
%o A289867 (Magma) [k: p in PrimesUpTo(800) | IsPrime(k) where k is Seqint(Intseq(p) cat [6])];
%o A289867 (PARI) terms(n) = my(i=0); forprime(p=1, , my(s=eval(Str(6, p))); if(ispseudoprime(s), print1(s, ", "); i++); if(i==n, break))
%o A289867 /* Print initial 50 terms as follows */
%o A289867 terms(50) \\ _Felix Fröhlich_, Jul 15 2017
%Y A289867 Cf. similar sequences listed in A289866.
%K A289867 nonn,base
%O A289867 1,1
%A A289867 _Vincenzo Librandi_, Jul 15 2017