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A014614 Numbers that are products of 5 primes (or 5-almost primes, a generalization of semiprimes). 90
32, 48, 72, 80, 108, 112, 120, 162, 168, 176, 180, 200, 208, 243, 252, 264, 270, 272, 280, 300, 304, 312, 368, 378, 392, 396, 405, 408, 420, 440, 450, 456, 464, 468, 496, 500, 520, 552, 567, 588, 592, 594, 612, 616, 630, 656, 660, 675, 680, 684, 688, 696 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Divisible by exactly 5 prime powers (not including 1).
LINKS
Eric Weisstein's World of Mathematics, Almost Prime
FORMULA
Product p_i^e_i with sum e_i = 5.
a(n) ~ 24n log n/(log log n)^4. - Charles R Greathouse IV, Mar 20 2013
a(n) = A078840(5,n). - R. J. Mathar, Jan 30 2019
MATHEMATICA
Select[Range[300], Plus @@ Last /@ FactorInteger[ # ] == 5 &] (* Vladimir Joseph Stephan Orlovsky, Apr 23 2008 *)
PROG
(PARI) is(n)=bigomega(n)==5 \\ Charles R Greathouse IV, Mar 20 2013
CROSSREFS
Cf. A046304, A114453 (number of 5-almost primes <= 10^n).
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), this sequence (r = 5), A046306 (r = 6), A046308 (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: A090052 A163285 A036329 * A046371 A348824 A175162
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Scott Lindhurst (ScottL(AT)alumni.princeton.edu) and Patrick De Geest, Jun 15 1998
STATUS
approved

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Last modified March 19 04:58 EDT 2024. Contains 370952 sequences. (Running on oeis4.)