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 A171018 #14 Mar 31 2017 20:31:33
%S A171018 3,2,5,7,11,12,17,19,32,39,21,27,41,42,47,52,59,61,67,71,72,79,82,89,
%T A171018 97,101,102,107,109,112,137,121,127,129,149,151,157,162,167,172,179,
%U A171018 181,191,192,197,199,311,332,337,339,322,329,341,351,357,362
%N A171018 In the sequence of prime numbers, replace all the '3' digits with '2' and vice versa.
%H A171018 Vincenzo Librandi, <a href="/A171018/b171018.txt">Table of n, a(n) for n = 1..1000</a>
%t A171018 f[n_]:=FromDigits[(IntegerDigits[n]/.{2->a,3->b}) /.{a->3,b->2}]; f/@Prime[Range[80]] (* _Harvey P. Dale_, Apr 01 2011 *)
%o A171018 (PARI) a(n)=my(v=[0,1,3,2,4,5,6,7,8,9]);apply(k->v[k+1],digits(prime(n))) \\ _Charles R Greathouse IV_, Jul 16 2013
%K A171018 nonn,base,easy
%O A171018 1,1
%A A171018 _N. J. A. Sloane_ and _Vincenzo Librandi_, Sep 04 2010