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A069279 18-almost 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).

Any 18-almost prime can be represented in several ways as a product of two 9-almost primes A046312; in several ways as a product of three 6-almost primes A046306; in several ways as a product of six 3-almost primes A014612; and in several ways as a product of nine semiprimes A001358. - Jonathan Vos Post, Dec 12 2004

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.

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 July 22 22:07 EDT 2014. Contains 244844 sequences.