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 A039216 #26 Jun 26 2021 15:47:30
%S A039216 1,2,3,4,5,6,8,9,10,11,13,14,15,16,17,18,20,21,22,23,25,26,27,28,29,
%T A039216 30,32,33,34,35,37,38,39,40,41,42,44,45,46,47,49,50,51,52,53,54,56,57,
%U A039216 58,59,61,62,63,64,65,66,68,69,70,71,73,74,75,76,77,78,80,81,82,83
%N A039216 Numbers whose base-12 representation has the same number of 0's and 7's.
%H A039216 David A. Corneth, <a href="/A039216/b039216.txt">Table of n, a(n) for n = 1..10000</a>
%o A039216 (PARI) f(n, b, d)=#select(x->x==d, digits(n, b));
%o A039216 for(n=1, 110, if (f(n, 12, 0)==f(n, 12, 7), print1(n, ", ")));\\ _Petros Hadjicostas_, Jul 08 2020
%o A039216 (PARI) is(n) = {my(d = digits(n, 12), v = vector(12)); for(i = 1, #d, v[d[i]+1]++); v[1]==v[8]} \\ _David A. Corneth_, Jul 09 2020
%K A039216 nonn,base,easy
%O A039216 1,2
%A A039216 _Olivier Gérard_