A039700 - OEIS

%I #18 Jul 30 2021 06:21:19

%S 1,3,18,36,45,63,72,99,117,144,153,171,207,225,261,270,279,288,333,

%T 369,378,387,423,441,477,531,540,549,576,594,603,639,657,702,711,747,

%U 756,801,873,909,918,927,945,963,981,1017,1026,1080,1089,1125,1143,1152

%N Numbers k such that the largest power of 3 dividing k equals 3^omega(k).

%C Here, "omega(k)" means the number of prime factors of k counted without multiplicity. - _Harvey P. Dale_, Sep 30 2015

%H Harvey P. Dale, <a href="/A039700/b039700.txt">Table of n, a(n) for n = 1..1000</a>

%e omega(18)=2 and 9=3^2 is the largest power of 3 dividing 18, hence 18 is in the sequence.

%t Select[Range[1200],IntegerExponent[#,3]==PrimeNu[#]&] (* _Harvey P. Dale_, Sep 30 2015 *)

%Y Cf. A001221 (omega), A038500, A023534 (similar for powers of 2).

%K nonn

%O 1,2

%A _Benoit Cloitre_, Sep 04 2002