A123321 Products of 7 distinct primes (squarefree 7-almost primes).

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

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