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A102440 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(3*3*11) -> 3*3*[11->2*5] = 3*3*2*5 = 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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