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 A004726 #19 Jul 13 2025 13:11:55
%S A004726 0,1,2,3,4,5,6,8,9,10,11,12,13,14,15,16,1,18,19,20,21,22,23,24,25,26,
%T A004726 2,28,29,30,31,32,33,34,35,36,3,38,39,40,41,42,43,44,45,46,4,48,49,50,
%U A004726 51,52,53,54,55,56,5,58,59,60,61,62,63,64,65,66,6,68,69,0,1,2
%N A004726 Delete all 7's from the sequence of nonnegative integers.
%t A004726 Delete[Table[FromDigits[IntegerDigits[n]/.(7->Nothing)],{n,0,80}],8] (* _Harvey P. Dale_, Jul 13 2025 *)
%o A004726 (Python)
%o A004726 def A004726(n):
%o A004726 l = len(str(n))
%o A004726 m = 7*(10**l-1)//9
%o A004726 k = n + l - int(n+l < m)
%o A004726 return 6 if k == m else int(str(k).replace('7','')) # _Chai Wah Wu_, Apr 20 2021
%Y A004726 Cf. A004719, A004720, A004721, A004722, A004723, A004724, A004725, A004727, A004728.
%K A004726 base,nonn
%O A004726 0,3
%A A004726 _N. J. A. Sloane_