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%I #15 Apr 25 2024 06:35:33
%S 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,
%T 42,44,45,47,51,52,55,57,58,59,60,61,64,70,71,72,73,74,75,76,77,78,79,
%U 81,96,99,102,104,105,106,109,112,116,127,131,132,133,134,135,136
%N Exponents k such that the binary expansion of 3^k has an even number of ones.
%H Hugo Pfoertner, <a href="/A371970/b371970.txt">Table of n, a(n) for n = 1..10000</a>
%p q:= n-> is(add(i, i=Bits[Split](3^n))::even):
%p select(q, [$0..150])[]; # _Alois P. Heinz_, Apr 24 2024
%t Select[Range[136], EvenQ@ DigitCount[3^#, 2, 1] &] (* _Michael De Vlieger_, Apr 24 2024 *)
%o (PARI) is_a371970(k) = hammingweight(3^k)%2 == 0
%Y Complement of A223024.
%Y Cf. A000120, A000244, A001969, A011754, A078839.
%K nonn,base,easy
%O 1,2
%A _Hugo Pfoertner_, Apr 24 2024