A237545 Odious powers of 3.

1, 81, 2187, 59049, 177147, 1594323, 14348907, 43046721, 1162261467, 3486784401, 31381059609, 22876792454961, 68630377364883, 205891132094649, 16677181699666569, 150094635296999121, 36472996377170786403, 328256967394537077627, 8862938119652501095929, 79766443076872509863361

Offset

1,2

Comments

Intersection of A000069 and A000244.

Exponents of a(n): A223024.

It seems that this sequence includes about half of the powers of 3. For example, a(50171) = 3^99999. - Charles R Greathouse IV, Mar 05 2014

Links

Robert Israel, Table of n, a(n) for n = 1..1058

Maple

select(t -> convert(convert(t, base, 2), `+`)::odd, [seq(3^i, i=0..100)]); # Robert Israel, Oct 10 2016

Mathematica

Select[3^Range[32], OddQ[First[DigitCount[#, 2] ] ]&] (* Wouter Meeussen, Feb 09 2014 *)

Prog

(PARI) for(n=0, 100, if(hammingweight(t=3^n)%2, print1(t", "))) \\ Charles R Greathouse IV, Mar 05 2014

Crossrefs

Cf. A000069 (odious numbers), A000244 (powers of 3), A223024.

Sequence in context: A237316 A237722 A250436 * A253399 A236820 A370229

Adjacent sequences: A237542 A237543 A237544 * A237546 A237547 A237548

Keyword

nonn,easy

Author

Ilya Lopatin and Juri-Stepan Gerasimov, Feb 09 2014

Extensions

Corrected and more terms added by Robert Israel, Oct 10 2016

Status

approved