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A069276 15-almost primes (generalization of semiprimes). 29
32768, 49152, 73728, 81920, 110592, 114688, 122880, 165888, 172032, 180224, 184320, 204800, 212992, 248832, 258048, 270336, 276480, 278528, 286720, 307200, 311296, 319488, 373248, 376832, 387072, 401408, 405504, 414720, 417792, 430080 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Product of 15 not necessarily distinct primes.
Divisible by exactly 15 prime powers (not including 1).
Any 15-almost prime can be represented in several ways as a product of three 5-almost primes A014614, and in several ways as a product of five 3-almost primes A014612. - Jonathan Vos Post, Dec 11 2004
LINKS
Eric Weisstein's World of Mathematics, Almost Prime.
FORMULA
Product p_i^e_i with Sum e_i = 15.
MATHEMATICA
Select[Range[90000], Plus @@ Last /@ FactorInteger[ # ] == 15 &] (* Vladimir Joseph Stephan Orlovsky, Apr 23 2008 *)
Select[Range[450000], PrimeOmega[#]==15&] (* Harvey P. Dale, Aug 14 2019 *)
PROG
(PARI) k=15; start=2^k; finish=500000; v=[] for(n=start, finish, if(bigomega(n)==k, v=concat(v, n))); v
CROSSREFS
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), A046308 (r = 7), A046310 (r = 8), A046312 (r = 9), A046314 (r = 10), A069272 (r = 11), A069273 (r = 12), A069274 (r = 13), A069275 (r = 14), this sequence (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: A222528 A232393 A217589 * A195235 A223335 A194934
KEYWORD
nonn
AUTHOR
Rick L. Shepherd, Mar 13 2002
STATUS
approved

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Last modified March 19 04:26 EDT 2024. Contains 370952 sequences. (Running on oeis4.)