id:A109313 - OEIS Search Results

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Difference between prime factors of n-th semiprime.

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0, 1, 0, 3, 5, 2, 4, 9, 0, 11, 8, 15, 2, 17, 10, 21, 0, 14, 6, 16, 27, 29, 8, 20, 35, 4, 39, 12, 41, 26, 6, 28, 45, 14, 51, 34, 18, 57, 10, 0, 59, 38, 40, 12, 65, 44, 69, 2, 24, 71, 26, 77, 50, 16, 81, 0, 56, 87, 58, 32, 6, 95, 64, 99, 22, 36, 101, 8, 68, 105, 38, 24, 107, 70, 4 (list; graph; listen)

	OFFSET	`1,4`
	COMMENT	`a(n)=0 if sp(n) is a square of prime. Cf. A068318 Sum of prime factors of n-th semiprime.`
	LINKS	`Zak Seidov, Table of n, a(n) for n = 1..1000`
	EXAMPLE	`a(1)=0 because sp(1)=4=22 and 2-2=0; a(2)=1 because sp(2)=6=23 and 3-2=1; sp(n)=n-th semiprime.`
	MAPLE	`with(numtheory): a:=proc(n) if bigomega(n)=2 and nops(factorset(n))=2 then factorset(n)[2]-factorset(n)[1] elif bigomega(n)=2 then 0 else fi end: seq(a(n), n=1..225); (Emeric Deutsch)`
	CROSSREFS	`Cf. A068318.` `Sequence in context: A084753 A163364 A082822 this_sequence A065188 A065257 A090396` `Adjacent sequences: A109310 A109311 A109312 this_sequence A109314 A109315 A109316`
	KEYWORD	`nonn`
	AUTHOR	`Zak Seidov (zakseidov(AT)yahoo.com), Jun 27 2005`

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Last modified December 17 23:40 EST 2009. Contains 171025 sequences.

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