login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A168645 Numbers with 2 or 3 prime divisors (counted with multiplicity). 0
4, 6, 8, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 27, 28, 30, 33, 34, 35, 38, 39, 42, 44, 45, 46, 49, 50, 51, 52, 55, 57, 58, 62, 63, 65, 66, 68, 69, 70, 74, 75, 76, 77, 78, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 102, 105, 106, 110, 111, 114, 115, 116, 117, 118, 119 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Below 32 this sequence and A063989 are identical.

LINKS

Table of n, a(n) for n=1..67.

MATHEMATICA

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

PROG

(PARI) is(n)=my(t=bigomega(n)); t==2 || t==3 \\ Charles R Greathouse IV, Jun 19 2016

CROSSREFS

Cf. A001222, A063989.

Sequence in context: A063806 A323521 A063989 * A282668 A117097 A077135

Adjacent sequences:  A168642 A168643 A168644 * A168646 A168647 A168648

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Dec 01 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 6 16:34 EDT 2020. Contains 334828 sequences. (Running on oeis4.)