id:A102440 - OEIS Search Results

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Replace each prime factor of n that is greater than 3 by the greatest semiprime less than it.

+0
6

1, 2, 3, 4, 4, 6, 6, 8, 9, 8, 10, 12, 10, 12, 12, 16, 15, 18, 15, 16, 18, 20, 22, 24, 16, 20, 27, 24, 26, 24, 26, 32, 30, 30, 24, 36, 35, 30, 30, 32, 39, 36, 39, 40, 36, 44, 46, 48, 36, 32, 45, 40, 51, 54, 40, 48, 45, 52, 58, 48, 58, 52, 54, 64, 40, 60, 65, 60, 66, 48, 69, 72, 69 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`a(n)<=n and a(n)=n iff n is 3-smooth, see A003586;` `A102441(n)=a(a(n)), see A102442, A102443 for iterations.`
	FORMULA	`Multiplicative with prime(i) -> (if i<=2 then prime(i) else A102415(i)).`
	EXAMPLE	`a(99) = a(3311) -> 33[11->25] = 3325 = 90.`
	CROSSREFS	`Sequence in context: A003962 A102443 A102441 this_sequence A124815 A081328 A072455` `Adjacent sequences: A102437 A102438 A102439 this_sequence A102441 A102442 A102443`
	KEYWORD	`nonn,mult`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jan 09 2005`

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Last modified November 23 10:40 EST 2009. Contains 167421 sequences.

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