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A237545 Odious powers of 3. 2
1, 81, 2187, 59049, 177147, 1594323, 14348907, 43046721, 1162261467, 3486784401, 31381059609, 22876792454961, 68630377364883, 205891132094649, 16677181699666569, 150094635296999121, 36472996377170786403, 328256967394537077627, 8862938119652501095929, 79766443076872509863361 (list; graph; refs; listen; history; text; internal format)
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 A237464

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

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Last modified November 17 00:14 EST 2018. Contains 317275 sequences. (Running on oeis4.)