id:A081060 - OEIS Search Results

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Product of differences of distinct prime factors of n.

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3

1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 2, 1, 1, 1, 1, 3, 4, 9, 1, 1, 1, 11, 1, 5, 1, 6, 1, 1, 8, 15, 2, 1, 1, 17, 10, 3, 1, 20, 1, 9, 2, 21, 1, 1, 1, 3, 14, 11, 1, 1, 6, 5, 16, 27, 1, 6, 1, 29, 4, 1, 8, 72, 1, 15, 20, 30, 1, 1, 1, 35, 2, 17, 4, 110, 1, 3, 1, 39, 1, 20, 12, 41, 26, 9, 1, 6, 6, 21, 28 (list; graph; listen)

	OFFSET	`1,10`
	COMMENT	`a(n)=1 iff n is 3-smooth (A003586) or n is a prime power (A000961), see A081061;` `a(A006881(k))>1 for k>1; if a(n)>1 then A079275(n)>0.`
	FORMULA	`a(n) = Product(abs(p-q): p, q distinct prime factors of n).`
	EXAMPLE	`a(42) = a(237) = \|2-3\|\|2-7\|\|3-7\| = 154 = 20.`
	CROSSREFS	`Sequence in context: A119288 A028234 A052125 this_sequence A131268 A109221 A046643` `Adjacent sequences: A081057 A081058 A081059 this_sequence A081061 A081062 A081063`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 04 2003`

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Last modified December 4 15:11 EST 2009. Contains 170347 sequences.

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