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 A171050 #11 Mar 31 2017 00:47:23
%S A171050 2,3,5,7,99,93,97,91,23,21,39,37,49,43,47,53,51,69,67,79,73,71,83,81,
%T A171050 17,909,903,907,901,993,927,939,937,931,941,959,957,963,967,973,971,
%U A171050 989,919,913,917,911,299,223,227,221,233,231,249,259,257,263
%N A171050 In the sequence of prime numbers, replace all the '9' digits with '1' and vice versa.
%H A171050 Vincenzo Librandi, <a href="/A171050/b171050.txt">Table of n, a(n) for n = 1..1000</a>
%t A171050 FromDigits[IntegerDigits[#] /. {9 -> p, 1 -> q} /. {p -> 1, q -> 9}] & /@ Prime[Range[100]] (* _Vincenzo Librandi_, Apr 07 2013 *)
%o A171050 (PARI) a(n)=my(v=[0,9,2,3,4,5,6,7,8,1]);subst(Pol(apply(k->v[k+1], digits(prime(n)))),'x,10) \\ _Charles R Greathouse IV_, Jul 31 2013
%K A171050 nonn,base,easy
%O A171050 1,1
%A A171050 _N. J. A. Sloane_ and _Vincenzo Librandi_, Sep 04 2010