A044995 Numbers whose base-3 representation contains exactly one 0 and one 2.

6, 11, 15, 19, 21, 32, 34, 38, 42, 46, 48, 58, 64, 66, 95, 97, 103, 113, 115, 119, 123, 127, 129, 139, 145, 147, 175, 193, 199, 201, 284, 286, 292, 310, 338, 340, 346, 356, 358, 362, 366, 370, 372, 382, 388, 390, 418, 436, 442, 444

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base
• look

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A039276.

Cf. A007089, A005823.

Programs

Maple

F:= proc(n) local i,j,t;
t:= (3^n-1)/2;
op(sort([seq(seq(t - 3^i + 3^j, i= {$0..j-1, $j+1..n-2}),j=0..n-1)]))
end proc:
map(F, [$2..7]); # Robert Israel, Mar 11 2020

Mathematica

Select[Range[500],DigitCount[#,3,0]==DigitCount[#,3,2]==1&] (* Harvey P. Dale, Sep 04 2023 *)

Python

from sympy.ntheory import count_digits
def ok(n): d = count_digits(n, 3); return d[0] == 1 and d[2] == 1
print(list(filter(ok, range(500)))) # Michael S. Branicky, Jun 11 2021