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 A031953 #16 Aug 10 2021 11:07:35 %S A031953 8,10,11,12,13,14,15,16,17,19,20,21,22,23,24,25,26,28,29,30,31,32,33, %T A031953 34,35,37,38,39,40,41,42,43,44,46,47,48,49,50,51,52,53,55,56,57,58,59, %U A031953 60,61,62,64,65,72,74,75,76,77,78,79,81,82,89,91,97,100,105 %N A031953 Numbers with exactly two distinct base-8 digits. %H A031953 <a href="/index/Ar#2-automatic">Index entries for 2-automatic sequences</a>. %t A031953 Select[Range[100],Length[Union[IntegerDigits[#,8]]]==2&] (* _Harvey P. Dale_, Feb 15 2019 *) %o A031953 (PARI) is(n)=#Set(digits(n, 8))==2 \\ _Charles R Greathouse IV_, Feb 15 2017 %o A031953 (Python) %o A031953 def ok(n): return len(set(oct(n)[2:])) == 2 %o A031953 print(list(filter(ok, range(106)))) # _Michael S. Branicky_, Aug 10 2021 %Y A031953 Cf. A031948 - A031955. %K A031953 nonn,base,easy %O A031953 1,1 %A A031953 _Clark Kimberling_ %E A031953 Name edited by _Michael S. Branicky_, Aug 10 2021