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 A222240 #11 Mar 31 2017 00:17:25
%S A222240 0,1,2,3,5,4,6,7,8,9,10,11,12,13,15,14,16,17,18,19,20,21,22,23,25,24,
%T A222240 26,27,28,29,30,31,32,33,35,34,36,37,38,39,50,51,52,53,55,54,56,57,58,
%U A222240 59,40,41,42,43,45,44,46,47,48,49,60,61,62,63,65,64,66,67,68,69,70,71,72,73,75,74
%N A222240 In the number n, replace all (decimal) digits '4' with '5' and vice versa.
%C A222240 The map which is applied to primes in A171027.
%H A222240 Vincenzo Librandi, <a href="/A222240/b222240.txt">Table of n, a(n) for n = 0..1000</a>
%t A222240 a[n_]:= IntegerDigits[n]/.{4->5, 5->4} // FromDigits; Table[a[n], {n, 0, 80}] (* _Vincenzo Librandi_, Jul 31 2013 *)
%o A222240 (PARI) A222240(n,d=[0, 1, 2, 3, 5, 4, 6, 7, 8, 9])={sum(i=1,#n=digits(n),d[n[i]+1]*10^(#n-i),!n*d[1])} \\ N.B.: digits(0)=[] in PARI (v.2.6)
%Y A222240 Cf. A222210-A222254; A171013-A171016, A175770, A171018-A171057.
%K A222240 nonn,base,easy
%O A222240 0,3
%A A222240 _M. F. Hasler_, Feb 13 2013