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A123321 Products of 7 distinct primes (squarefree 7-almost primes). 8
510510, 570570, 690690, 746130, 870870, 881790, 903210, 930930, 1009470, 1067430, 1111110, 1138830, 1193010, 1217370, 1231230, 1272810, 1291290, 1345890, 1360590, 1385670, 1411410, 1438710, 1452990, 1504230, 1540770 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Intersection of A005117 and A046308.

Intersection of A005117 and A176655. - R. J. Mathar, Dec 05 2016

LINKS

Rick L. Shepherd, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1) = 510510 = 2*3*5*7*11*13*17 = A002110(7).

MATHEMATICA

f7Q[n_]:=Last/@FactorInteger[n]=={1, 1, 1, 1, 1, 1, 1}; lst={}; Do[If[f7Q[n], AppendTo[lst, n]], {n, 9!}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 26 2008 *)

Select[Range[1600000], PrimeNu[#]==7&&SquareFreeQ[#]&] (* Harvey P. Dale, Sep 19 2013 *)

PROG

(PARI) is(n)=omega(n)==7 && bigomega(n)==7 \\ Hugo Pfoertner, Dec 18 2018

CROSSREFS

Cf. A005117, A046308, A048692, Squarefree k-almost primes: A000040 (k=1), A006881 (k=2), A007304 (k=3), A046386 (k=4), A046387 (k=5), A067885 (k=6), A123322 (k=8), A115343 (k=9).

Sequence in context: A250057 A230619 A176655 * A258362 A147574 A046325

Adjacent sequences:  A123318 A123319 A123320 * A123322 A123323 A123324

KEYWORD

nonn

AUTHOR

Rick L. Shepherd, Sep 25 2006

EXTENSIONS

More terms from Vladimir Joseph Stephan Orlovsky, Aug 26 2008

STATUS

approved

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Last modified October 17 14:28 EDT 2019. Contains 328114 sequences. (Running on oeis4.)