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 A069832 #11 Oct 14 2019 07:30:48
%S A069832 1,3,9,19,27,33,39,57,87,97,159,177,187,433,487,541,603,691,717,753,
%T A069832 757,853,949,1257,1471,1707,2277,2367,2617,2953,4317,4507,4623,4779,
%U A069832 4797,5773,6481,6757,6777,7017,7351,7417,7471,7479,7747,7797,7813,7977
%N A069832 Prefixing, suffixing or inserting a 7 in the number anywhere gives a prime.
%H A069832 Giovanni Resta, <a href="/A069832/b069832.txt">Table of n, a(n) for n = 1..2399</a> (terms < 10^13, first 201 terms from Harvey P. Dale)
%t A069832 psi7Q[n_]:=Module[{idn=IntegerDigits[n]},And@@PrimeQ[FromDigits/@ Table[ Insert[ idn,7,i],{i,Length[idn]+1}]]]; Select[Range[8000],psi7Q] (* _Harvey P. Dale_, Sep 18 2012 *)
%Y A069832 Cf. A068674, A068679, A069833.
%K A069832 base,nonn
%O A069832 1,2
%A A069832 _Amarnath Murthy_, Apr 14 2002
%E A069832 More terms from _Vladeta Jovovic_, Apr 16 2002
%E A069832 Offset changed to 1 by _Giovanni Resta_, Oct 14 2019