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A168645 Numbers with 2 or 3 prime divisors (counted with multiplicity). 0

%I

%S 4,6,8,9,10,12,14,15,18,20,21,22,25,26,27,28,30,33,34,35,38,39,42,44,

%T 45,46,49,50,51,52,55,57,58,62,63,65,66,68,69,70,74,75,76,77,78,82,85,

%U 86,87,91,92,93,94,95,98,99,102,105,106,110,111,114,115,116,117,118,119

%N Numbers with 2 or 3 prime divisors (counted with multiplicity).

%C Below 32 this sequence and A063989 are identical.

%t Select[Range[150],MemberQ[{2,3},Total[Transpose[ FactorInteger[#]] [[2]]]]&] (* _Harvey P. Dale_, Mar 28 2011 *)

%o (PARI) is(n)=my(t=bigomega(n)); t==2 || t==3 \\ _Charles R Greathouse IV_, Jun 19 2016

%Y Cf. A001222, A063989.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Dec 01 2009

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Last modified May 8 02:26 EDT 2021. Contains 343652 sequences. (Running on oeis4.)