id:A125604 - OEIS Search Results

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Minimum of the largest prime factors of a number and its two neighbors.

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2, 2, 2, 3, 2, 2, 2, 3, 3, 3, 3, 5, 2, 2, 2, 3, 3, 5, 5, 7, 3, 3, 3, 3, 3, 3, 5, 5, 2, 2, 2, 7, 3, 3, 3, 13, 5, 5, 5, 7, 7, 5, 5, 5, 3, 3, 3, 5, 5, 13, 3, 3, 3, 7, 7, 19, 5, 5, 5, 7, 2, 2, 2, 11, 11, 17, 7, 7, 3, 3, 3, 5, 5, 5, 11, 11, 5, 3, 3, 3, 7, 7, 7, 17, 11, 11, 5, 5, 5, 13, 23, 19, 3, 3, 3, 7, 5, 5 (list; graph; listen)

	OFFSET	`3,1`
	FORMULA	`a(n)=min{lpf(n-1),lpf(n),lpf(n+1)}, where lpf is the largest prime factor: lpf(k)=A006530(n).`
	EXAMPLE	`a(93) = min{lpf(92),lpf(93),lpf(94)} = min{23,31,47} = 23.`
	MATHEMATICA	`LPF = FactorInteger[ # ][[ -1, 1]] &; Map[Min[{LPF[ # - 1], LPF[ # ], LPF[ # + 1]}] &, Range[3, 200]]`
	CROSSREFS	`Cf. A093074.` `Sequence in context: A065569 A127656 A109709 this_sequence A135592 A022912 A022922` `Adjacent sequences: A125601 A125602 A125603 this_sequence A125605 A125606 A125607`
	KEYWORD	`nonn`
	AUTHOR	`Carlos Alves (cjsalves(AT)gmail.com), Nov 27 2006`

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Last modified December 3 16:57 EST 2008. Contains 151279 sequences.

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