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 A046308 Numbers that are divisible by exactly 7 primes counting multiplicity. 53
 128, 192, 288, 320, 432, 448, 480, 648, 672, 704, 720, 800, 832, 972, 1008, 1056, 1080, 1088, 1120, 1200, 1216, 1248, 1458, 1472, 1512, 1568, 1584, 1620, 1632, 1680, 1760, 1800, 1824, 1856, 1872, 1984, 2000, 2080, 2187, 2208, 2268, 2352, 2368, 2376 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also called 7-almost primes. Products of exactly 7 primes (not necessarily distinct). - Jonathan Vos Post, Dec 11 2004 Also, positions of 7 in A001222. - Zak Seidov, Oct 14 2012 LINKS T. D. Noe, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Reference FORMULA Product p_i^e_i with sum e_i = 7. a(n) ~ 720n log n / (log log n)^6. - Charles R Greathouse IV, May 06 2013 a(n) = A078840(7,n). - R. J. Mathar, Jan 30 2019 MATHEMATICA Select[Range, Plus @@ Last /@ FactorInteger[ # ] == 7 &] (* Vladimir Joseph Stephan Orlovsky, Apr 23 2008 *) PROG (PARI) is(n)=bigomega(n)==7 \\ Charles R Greathouse IV, Mar 21 2013 CROSSREFS Cf. A120048 (number of 7-almost primes <= 10^n). Cf. A101605, A101606, A001222. Sequences listing r-almost primes, that is, the n such that A001222(n) = r: A000040 (r = 1), A001358 (r = 2), A014612 (r = 3), A014613 (r = 4), A014614 (r = 5), A046306 (r = 6), this sequence (r = 7), A046310 (r = 8), A046312 (r = 9), A046314 (r = 10), A069272 (r = 11), A069273 (r = 12), A069274 (r = 13), A069275 (r = 14), A069276 (r = 15), A069277 (r = 16), A069278 (r = 17), A069279 (r = 18), A069280 (r = 19), A069281 (r = 20). - Jason Kimberley, Oct 02 2011 Sequence in context: A114418 A046307 A036331 * A110290 A045028 A255997 Adjacent sequences:  A046305 A046306 A046307 * A046309 A046310 A046311 KEYWORD nonn AUTHOR Patrick De Geest, Jun 15 1998 STATUS approved

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Last modified June 24 06:17 EDT 2021. Contains 345416 sequences. (Running on oeis4.)