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 A171026 #9 Mar 31 2017 20:27:28
%S A171026 2,5,3,7,11,15,17,19,25,29,51,57,41,45,47,35,39,61,67,71,75,79,85,89,
%T A171026 97,101,105,107,109,115,127,151,157,159,149,131,137,165,167,175,179,
%U A171026 181,191,195,197,199,211,225,227,229,255,259,241,231,237,265
%N A171026 In the sequence of prime numbers, replace all the '5' digits with '3' and vice versa.
%H A171026 Vincenzo Librandi, <a href="/A171026/b171026.txt">Table of n, a(n) for n = 1..1000</a>
%t A171026 FromDigits[IntegerDigits[#]/.{5->p, 3->q}/.{p->3, q->5}]&/@Prime[Range[100]] (* _Vincenzo Librandi_, Apr 07 2013 *)
%o A171026 (PARI) a(n)=my(v=[0,1,2,5,4,3,6,7,8,9]);subst(Pol(apply(k->v[k+1], digits(prime(n)))),'x,10) \\ _Charles R Greathouse IV_, Jul 24 2013
%K A171026 nonn,base,easy
%O A171026 1,1
%A A171026 _N. J. A. Sloane_ and _Vincenzo Librandi_, Sep 04 2010