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 A044995 #28 Sep 04 2023 16:53:02
%S A044995 6,11,15,19,21,32,34,38,42,46,48,58,64,66,95,97,103,113,115,119,123,
%T A044995 127,129,139,145,147,175,193,199,201,284,286,292,310,338,340,346,356,
%U A044995 358,362,366,370,372,382,388,390,418,436,442,444
%N A044995 Numbers whose base-3 representation contains exactly one 0 and one 2.
%H A044995 Robert Israel, <a href="/A044995/b044995.txt">Table of n, a(n) for n = 1..10000</a>
%p A044995 F:= proc(n) local i,j,t;
%p A044995 t:= (3^n-1)/2;
%p A044995 op(sort([seq(seq(t - 3^i + 3^j, i= {$0..j-1, $j+1..n-2}),j=0..n-1)]))
%p A044995 end proc:
%p A044995 map(F, [$2..7]); # _Robert Israel_, Mar 11 2020
%t A044995 Select[Range[500],DigitCount[#,3,0]==DigitCount[#,3,2]==1&] (* _Harvey P. Dale_, Sep 04 2023 *)
%o A044995 (Python)
%o A044995 from sympy.ntheory import count_digits
%o A044995 def ok(n): d = count_digits(n, 3); return d[0] == 1 and d[2] == 1
%o A044995 print(list(filter(ok, range(500)))) # _Michael S. Branicky_, Jun 11 2021
%Y A044995 Subsequence of A039276.
%Y A044995 Cf. A007089, A005823.
%K A044995 nonn,base,look
%O A044995 1,1
%A A044995 _Clark Kimberling_