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 A222237 #13 Jan 23 2018 06:51:09
%S A222237 0,1,2,7,4,5,6,3,8,9,10,11,12,17,14,15,16,13,18,19,20,21,22,27,24,25,
%T A222237 26,23,28,29,70,71,72,77,74,75,76,73,78,79,40,41,42,47,44,45,46,43,48,
%U A222237 49,50,51,52,57,54,55,56,53,58,59,60,61,62,67,64,65,66,63,68,69,30,31,32,37,34,35
%N A222237 In the number n, replace all (decimal) digits '3' with '7' and vice versa.
%C A222237 The map which is applied to primes in A171037.
%H A222237 Vincenzo Librandi, <a href="/A222237/b222237.txt">Table of n, a(n) for n = 0..1000</a>
%t A222237 a[n_]:= IntegerDigits[n]/.{3->7, 7->3} // FromDigits; Table[a[n], {n, 0, 80}] (* _Vincenzo Librandi_, Jul 30 2013 *)
%o A222237 (PARI) A222237(n,d=[0, 1, 2, 7, 4, 5, 6, 3, 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 A222237 Cf. A222210-A222254; A171013-A171016, A175770, A171018-A171057.
%K A222237 nonn,base,easy
%O A222237 0,3
%A A222237 _M. F. Hasler_, Feb 13 2013