id:A116199 - OEIS Search Results

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a(n) = the number of positive divisors of n which are coprime to sigma(n) = A000203(n).

+0
2

1, 2, 2, 3, 2, 1, 2, 4, 3, 2, 2, 2, 2, 2, 2, 5, 2, 2, 2, 2, 4, 2, 2, 1, 3, 2, 4, 1, 2, 2, 2, 6, 2, 2, 4, 9, 2, 2, 4, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 6, 2, 2, 2, 1, 4, 2, 4, 2, 2, 2, 2, 2, 6, 7, 4, 2, 2, 2, 2, 4, 2, 4, 2, 2, 6, 2, 4, 2, 2, 2, 5, 2, 2, 2, 4, 2, 2, 2, 2, 2, 2, 2, 4, 2, 2, 1, 2, 6, 2, 9, 2, 2, 2, 2, 4 (list; graph; listen)

	OFFSET	`1,2`
	EXAMPLE	`The sum of the positive divisors of 12 is 1+2+3+4+6+12 = 28. There are 2 positive divisors (1 and 3) of 12 which are coprime to 28. So a(12) = 2.`
	MAPLE	`with(numtheory): a:=proc(n) local div, ct, j: div:=divisors(n): ct:=0: for j from 1 to tau(n) do if igcd(div[j], sigma(n))=1 then ct:=ct+1 else ct:=ct fi od: ct: end: seq(a(n), n=1..140); - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 05 2007`
	CROSSREFS	`Cf. A128830.` `Sequence in context: A030362 A044050 A096826 this_sequence A092565 A021452 A093420` `Adjacent sequences: A116196 A116197 A116198 this_sequence A116200 A116201 A116202`
	KEYWORD	`nonn`
	AUTHOR	`Leroy Quet (qq-quet(AT)mindspring.com), Apr 16 2007`
	EXTENSIONS	`More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), May 05 2007`

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Last modified November 18 20:14 EST 2008. Contains 147244 sequences.

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