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 A222249 #10 Mar 30 2017 22:40:20
%S A222249 0,1,2,3,4,5,7,6,8,9,10,11,12,13,14,15,17,16,18,19,20,21,22,23,24,25,
%T A222249 27,26,28,29,30,31,32,33,34,35,37,36,38,39,40,41,42,43,44,45,47,46,48,
%U A222249 49,50,51,52,53,54,55,57,56,58,59,70,71,72,73,74,75,77,76,78,79,60,61,62,63,64,65
%N A222249 In the number n, replace all (decimal) digits '6' with '7' and vice versa.
%C A222249 The map which is applied to primes in A171040.
%H A222249 Vincenzo Librandi, <a href="/A222249/b222249.txt">Table of n, a(n) for n = 0..1000</a>
%t A222249 a[n_]:= IntegerDigits[n]/.{6->7, 7->6} // FromDigits; Table[a[n], {n, 0, 80}] (* _Vincenzo Librandi_, Jul 31 2013 *)
%o A222249 (PARI) A222249(n,d=[0, 1, 2, 3, 4, 5, 7, 6, 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 A222249 Cf. A222210-A222254; A171013-A171016, A175770, A171018-A171057.
%K A222249 nonn,base,easy
%O A222249 0,3
%A A222249 _M. F. Hasler_, Feb 13 2013