A371970 Exponents k such that the binary expansion of 3^k has an even number of ones.

1, 2, 3, 5, 6, 8, 9, 12, 14, 17, 18, 21, 23, 24, 25, 26, 27, 31, 32, 33, 35, 37, 38, 39, 40, 42, 44, 45, 47, 51, 52, 55, 57, 58, 59, 60, 61, 64, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 96, 99, 102, 104, 105, 106, 109, 112, 116, 127, 131, 132, 133, 134, 135, 136

Offset: 1

Author

Hugo Pfoertner, Apr 24 2024

Keywords

• nonn
• base
• easy

Links

• Hugo Pfoertner, Table of n, a(n) for n = 1..10000

Crossrefs

Complement of A223024.

Cf. A000120, A000244, A001969, A011754, A078839.

Programs

Maple

q:= n-> is(add(i, i=Bits[Split](3^n))::even):
select(q, [$0..150])[];  # Alois P. Heinz, Apr 24 2024

Mathematica

Select[Range[136], EvenQ@ DigitCount[3^#, 2, 1] &] (* Michael De Vlieger, Apr 24 2024 *)

PARI

is_a371970(k) = hammingweight(3^k)%2 == 0