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 A171025 #9 Mar 31 2017 20:28:02
%S A171025 5,3,2,7,11,13,17,19,53,59,31,37,41,43,47,23,29,61,67,71,73,79,83,89,
%T A171025 97,101,103,107,109,113,157,131,137,139,149,121,127,163,167,173,179,
%U A171025 181,191,193,197,199,511,553,557,559,533,539,541,521,527,563
%N A171025 In the sequence of prime numbers, replace all the '5' digits with '2' and vice versa.
%H A171025 Vincenzo Librandi, <a href="/A171025/b171025.txt">Table of n, a(n) for n = 1..1000</a>
%t A171025 FromDigits[IntegerDigits[#]/.{5->p, 2->q}/.{p->2, q->5}]&/@Prime[Range[100]] (* _Vincenzo Librandi_, Apr 07 2013 *)
%o A171025 (PARI) a(n)=my(v=[0,1,5,3,4,2,6,7,8,9]);subst(Pol(apply(k->v[k+1], digits(prime(n)))),'x,10) \\ _Charles R Greathouse IV_, Jul 16 2013
%K A171025 nonn,base,easy
%O A171025 1,1
%A A171025 _N. J. A. Sloane_ and _Vincenzo Librandi_, Sep 04 2010