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 A171036 #9 Mar 31 2017 11:10:05
%S A171036 7,3,5,2,11,13,12,19,73,79,31,32,41,43,42,53,59,61,62,21,23,29,83,89,
%T A171036 92,101,103,102,109,113,172,131,132,139,149,151,152,163,162,123,129,
%U A171036 181,191,193,192,199,711,773,772,779,733,739,741,751,752,763
%N A171036 In the sequence of prime numbers, replace all the '7' digits with '2' and vice versa.
%H A171036 Vincenzo Librandi, <a href="/A171036/b171036.txt">Table of n, a(n) for n = 1..1000</a>
%t A171036 FromDigits[IntegerDigits[#]/.{7->p, 2->q}/.{p->2, q->7}]&/@Prime[Range[100]] (* _Vincenzo Librandi_, Apr 07 2013 *)
%o A171036 (PARI) a(n)=my(v=[0,1,7,3,4,5,6,2,8,9]);subst(Pol(apply(k->v[k+1], digits(prime(n)))),'x,10) \\ _Charles R Greathouse IV_, Jul 25 2013
%K A171036 nonn,base,easy
%O A171036 1,1
%A A171036 _N. J. A. Sloane_ and _Vincenzo Librandi_, Sep 04 2010