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 A171039 #12 Mar 31 2017 11:07:25
%S A171039 2,3,7,5,11,13,15,19,23,29,31,35,41,43,45,73,79,61,65,51,53,59,83,89,
%T A171039 95,101,103,105,109,113,125,131,135,139,149,171,175,163,165,153,159,
%U A171039 181,191,193,195,199,211,223,225,229,233,239,241,271,275,263
%N A171039 In the sequence of prime numbers, replace all the '7' digits with '5' and vice versa.
%H A171039 Vincenzo Librandi, <a href="/A171039/b171039.txt">Table of n, a(n) for n = 1..1000</a>
%t A171039 pq[n_]:=Module[{idn=IntegerDigits[n]},FromDigits[idn/. {7->p,5->q}/. {p->5,q->7}]]; pq/@Prime[Range[60]] (* _Harvey P. Dale_, Apr 04 2011 *)
%o A171039 (PARI) a(n)=my(v=[0,1,2,3,4,7,6,5,8,9]);subst(Pol(apply(k->v[k+1], digits(prime(n)))),'x,10) \\ _Charles R Greathouse IV_, Jul 26 2013
%K A171039 nonn,base,easy
%O A171039 1,1
%A A171039 _N. J. A. Sloane_ and _Vincenzo Librandi_, Sep 04 2010