A044995 - OEIS

%I #28 Sep 04 2023 16:53:02

%S 6,11,15,19,21,32,34,38,42,46,48,58,64,66,95,97,103,113,115,119,123,

%T 127,129,139,145,147,175,193,199,201,284,286,292,310,338,340,346,356,

%U 358,362,366,370,372,382,388,390,418,436,442,444

%N Numbers whose base-3 representation contains exactly one 0 and one 2.

%H Robert Israel, <a href="/A044995/b044995.txt">Table of n, a(n) for n = 1..10000</a>

%p F:= proc(n) local i,j,t;

%p t:= (3^n-1)/2;

%p op(sort([seq(seq(t - 3^i + 3^j, i= {$0..j-1, $j+1..n-2}),j=0..n-1)]))

%p end proc:

%p map(F, [$2..7]); # _Robert Israel_, Mar 11 2020

%t Select[Range[500],DigitCount[#,3,0]==DigitCount[#,3,2]==1&] (* _Harvey P. Dale_, Sep 04 2023 *)

%o (Python)

%o from sympy.ntheory import count_digits

%o def ok(n): d = count_digits(n, 3); return d[0] == 1 and d[2] == 1

%o print(list(filter(ok, range(500)))) # _Michael S. Branicky_, Jun 11 2021

%Y Subsequence of A039276.

%Y Cf. A007089, A005823.

%K nonn,base,look

%O 1,1

%A _Clark Kimberling_