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 A171019 #9 Mar 31 2017 20:31:06
%S A171019 2,3,5,7,11,13,17,19,23,29,31,37,1,3,7,53,59,61,67,71,73,79,83,89,97,
%T A171019 141,143,147,149,113,127,131,137,139,109,151,157,163,167,173,179,181,
%U A171019 191,193,197,199,211,223,227,229,233,239,201,251,257,263,269
%N A171019 In the sequence of prime numbers, replace all the '4' digits with '0' and vice versa.
%H A171019 Vincenzo Librandi, <a href="/A171019/b171019.txt">Table of n, a(n) for n = 1..1000</a>
%t A171019 FromDigits[IntegerDigits[#]/.{4->p, 0->q}/.{p->0, q->4}]&/@Prime[Range[100]] (* _Vincenzo Librandi_, Apr 07 2013 *)
%o A171019 (PARI) a(n)=my(v=[4,1,2,3,0,5,6,7,8,9]);subst(Pol(apply(k->v[k+1], digits(prime(n)))),'x,10) \\ _Charles R Greathouse IV_, Jul 16 2013
%K A171019 nonn,base,easy
%O A171019 1,1
%A A171019 _N. J. A. Sloane_ and _Vincenzo Librandi_, Sep 04 2010