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A069279 Products of exactly 18 primes (generalization of semiprimes). 32
262144, 393216, 589824, 655360, 884736, 917504, 983040, 1327104, 1376256, 1441792, 1474560, 1638400, 1703936, 1990656, 2064384, 2162688, 2211840, 2228224, 2293760, 2457600, 2490368, 2555904, 2985984, 3014656, 3096576 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Product of 18 not necessarily distinct primes.
Divisible by exactly 18 prime powers (not including 1).
LINKS
Eric Weisstein's World of Mathematics, Almost Prime.
FORMULA
Product p_i^e_i with Sum e_i = 18.
MATHEMATICA
Select[Range[31*10^5], PrimeOmega[#]==18&] (* Harvey P. Dale, Apr 05 2015 *)
PROG
(PARI) k=18; start=2^k; finish=4000000; 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), A069276 (r = 15), A069277 (r = 16), A069278 (r = 17), this sequence (r = 18), A069280 (r = 19), A069281 (r = 20). - Jason Kimberley, Oct 02 2011
Sequence in context: A186873 A018867 A057445 * A068961 A224806 A224803
KEYWORD
nonn
AUTHOR
Rick L. Shepherd, Mar 13 2002
STATUS
approved

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Last modified March 19 01:22 EDT 2024. Contains 370952 sequences. (Running on oeis4.)