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A237545 Odious powers of 3. 2

%I #23 Jan 08 2018 01:58:32

%S 1,81,2187,59049,177147,1594323,14348907,43046721,1162261467,

%T 3486784401,31381059609,22876792454961,68630377364883,205891132094649,

%U 16677181699666569,150094635296999121,36472996377170786403,328256967394537077627,8862938119652501095929,79766443076872509863361

%N Odious powers of 3.

%C Intersection of A000069 and A000244.

%C Exponents of a(n): A223024.

%C 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

%H Robert Israel, <a href="/A237545/b237545.txt">Table of n, a(n) for n = 1..1058</a>

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

%t Select[3^Range[32],OddQ[First[DigitCount[#,2] ] ]&] (* _Wouter Meeussen_, Feb 09 2014 *)

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

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

%K nonn,easy

%O 1,2

%A _Ilya Lopatin_ and _Juri-Stepan Gerasimov_, Feb 09 2014

%E Corrected and more terms added by _Robert Israel_, Oct 10 2016

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Last modified March 29 06:34 EDT 2024. Contains 371265 sequences. (Running on oeis4.)