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A069279 Products of exactly 18 primes (generalization of semiprimes). 29
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

D. W. Wilson, Table of n, a(n) for n = 1..10000

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

Cf. A101637, A101638, A101605, A101606.

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

Adjacent sequences:  A069276 A069277 A069278 * A069280 A069281 A069282

KEYWORD

nonn

AUTHOR

Rick L. Shepherd, Mar 13 2002

STATUS

approved

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Last modified May 23 11:05 EDT 2017. Contains 286915 sequences.