

A075819


Even squarefree numbers with exactly 3 prime factors.


8



30, 42, 66, 70, 78, 102, 110, 114, 130, 138, 154, 170, 174, 182, 186, 190, 222, 230, 238, 246, 258, 266, 282, 286, 290, 310, 318, 322, 354, 366, 370, 374, 402, 406, 410, 418, 426, 430, 434, 438, 442, 470, 474, 494, 498, 506, 518, 530, 534, 574, 582, 590
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OFFSET

1,1


COMMENTS

This sequence first differs from A053858 at 2310=2*3*5*7*11, which is in A053858 but not in this sequence.


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000


EXAMPLE

30=2*3*5 and 42=2*3*7 are even, squarefree and have 3 prime factors.


MAPLE

ts_3_sod := proc(n); if (numtheory[bigomega](n)=3 and numtheory[mobius](n)=1 and type(n, even)='true') then RETURN(n); fi end: a3sod := [seq(ts_3_sod(i), i=1..2500)]: a3sod;


MATHEMATICA

Select[2*Range[300], SquareFreeQ[#]&&PrimeNu[#]==3&] (* Harvey P. Dale, Feb 16 2018 *)


PROG

(PARI) list(lim)=my(v=List()); forprime(p=5, lim\6, forprime(q=3, min(lim\(2*p), p2), listput(v, 2*p*q))); Set(v) \\ Charles R Greathouse IV, Aug 29 2017


CROSSREFS

Cf. A053858.
Sequence in context: A007304 A160350 A053858 * A306217 A034683 A328328
Adjacent sequences: A075816 A075817 A075818 * A075820 A075821 A075822


KEYWORD

easy,nonn


AUTHOR

Jani Melik, Oct 13 2002


EXTENSIONS

Edited by Dean Hickerson, Oct 21 2002


STATUS

approved



