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 A222251 #17 Sep 07 2021 09:26:09
%S A222251 0,1,2,3,4,5,9,7,8,6,10,11,12,13,14,15,19,17,18,16,20,21,22,23,24,25,
%T A222251 29,27,28,26,30,31,32,33,34,35,39,37,38,36,40,41,42,43,44,45,49,47,48,
%U A222251 46,50,51,52,53,54,55,59,57,58,56,90,91,92,93,94,95,99,97,98,96,70,71,72,73,74,75
%N A222251 In the number n, replace all (decimal) digits '6' with '9' and vice versa.
%C A222251 The map which is applied to primes in A171055.
%H A222251 Vincenzo Librandi, <a href="/A222251/b222251.txt">Table of n, a(n) for n = 0..1000</a>
%t A222251 a[n_]:= IntegerDigits[n]/.{6->9, 9->6} // FromDigits; Table[a[n], {n, 0, 80}] (* _Vincenzo Librandi_, Jul 31 2013 *)
%o A222251 (PARI) A222251(n,d=[0, 1, 2, 3, 4, 5, 9, 7, 8, 6])=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)
%o A222251 (Python)
%o A222251 def flp69(s): return s.replace("6", "-").replace("9", "6").replace("-", "9")
%o A222251 def aupto(lim): return [int(flp69(s)) for s in map(str, range(lim+1))]
%o A222251 print(aupto(75)) # _Michael S. Branicky_, Sep 07 2021
%Y A222251 Cf. A222210-A222254; A171013-A171016, A175770, A171018-A171057.
%K A222251 nonn,base,easy
%O A222251 0,3
%A A222251 _M. F. Hasler_, Feb 13 2013