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 A222231 #10 Mar 31 2017 00:22:17
%S A222231 0,1,7,3,4,5,6,2,8,9,10,11,17,13,14,15,16,12,18,19,70,71,77,73,74,75,
%T A222231 76,72,78,79,30,31,37,33,34,35,36,32,38,39,40,41,47,43,44,45,46,42,48,
%U A222231 49,50,51,57,53,54,55,56,52,58,59,60,61,67,63,64,65,66,62,68,69,20,21,27,23
%N A222231 In the number n, replace all (decimal) digits '2' with '7' and vice versa.
%C A222231 The map which is applied to primes in A171036.
%H A222231 Vincenzo Librandi, <a href="/A222231/b222231.txt">Table of n, a(n) for n = 0..1000</a>
%t A222231 a[n_]:= IntegerDigits[n]/.{2->7, 7->2} // FromDigits; Table[a[n], {n, 0, 80}] (* _Vincenzo Librandi_, Jul 30 2013 *)
%o A222231 (PARI) A222231(n,d=[0,1,7,3,4,5,6,2,8,9])=sum(i=1, #n=digits(n), d[n[i]+1]*10^(#n-i)) \\ gives correct value for n=0 iff d[1]=0, since digits(0)=[] in PARI (v.2.6)
%Y A222231 Cf. A222210-A222254; A171013-A171016, A175770, A171018-A171057.
%K A222231 nonn,base,easy
%O A222231 0,3
%A A222231 _M. F. Hasler_, Feb 12 2013