A014673 - OEIS

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A014673

Smallest prime factor of greatest proper divisor of n.

1, 1, 1, 2, 1, 3, 1, 2, 3, 5, 1, 2, 1, 7, 5, 2, 1, 3, 1, 2, 7, 11, 1, 2, 5, 13, 3, 2, 1, 3, 1, 2, 11, 17, 7, 2, 1, 19, 13, 2, 1, 3, 1, 2, 3, 23, 1, 2, 7, 5, 17, 2, 1, 3, 11, 2, 19, 29, 1, 2, 1, 31, 3, 2, 13, 3, 1, 2, 23, 5, 1, 2, 1, 37, 5, 2, 11, 3, 1, 2, 3, 41, 1, 2, 17, 43, 29, 2, 1, 3, 13, 2, 31, 47 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,4`
	COMMENTS	`a(n) = A020639(A032742(n));` `For n>1: a(n) = 1 iff n is prime; a(A001358(n)) = A084127(n); a(A000961(n)) = A020639(A000961(n)).`
	FORMULA	`A117357(n) = A020639(A054576(n)); A117358(n) = A032742(A054576(n)) = A054576(n)/A117357(n). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 10 2006`
	MATHEMATICA	`PrimeFactors[ n_ ] := Flatten[ Table[ # [ [ 1 ] ], {1} ] & /@ FactorInteger[ n ] ]; f[ n_ ] := Block[ {gpd = Divisors[ n ][ [ -2 ] ]}, If[ gpd == 1, 1, PrimeFactors[ gpd ][ [ 1 ] ] ] ]; Table[ If[ n == 1, 1, f[ n ] ], {n, 1, 95} ]`
	CROSSREFS	`Cf. A085392, A085393.` `Sequence in context: A096107 A128487 A056609 * A085392 A089384 A144113` `Adjacent sequences: A014670 A014671 A014672 * A014674 A014675 A014676`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 24 2003`

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Last modified February 16 21:51 EST 2012. Contains 205978 sequences.