id:A055212 - OEIS Search Results

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Number of composite divisors of n.

+0
4

0, 0, 0, 1, 0, 1, 0, 2, 1, 1, 0, 3, 0, 1, 1, 3, 0, 3, 0, 3, 1, 1, 0, 5, 1, 1, 2, 3, 0, 4, 0, 4, 1, 1, 1, 6, 0, 1, 1, 5, 0, 4, 0, 3, 3, 1, 0, 7, 1, 3, 1, 3, 0, 5, 1, 5, 1, 1, 0, 8, 0, 1, 3, 5, 1, 4, 0, 3, 1, 4, 0, 9, 0, 1, 3, 3, 1, 4, 0, 7, 3, 1, 0, 8, 1, 1, 1, 5, 0, 8, 1, 3, 1, 1, 1, 9, 0, 3, 3, 6, 0, 4, 0, 5, 4 (list; graph; listen)

	OFFSET	`1,8`
	LINKS	`Leroy Quet, Home Page (listed in lieu of email address)`
	FORMULA	`a(n)=tau(n)-omega(n)-1, where tau=A000005 and omega=A001221. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 13 2003`
	EXAMPLE	`a[20] = 3 because the composite divisors of 20 are 4, 10, 20.`
	MATHEMATICA	`Table[ Count[ PrimeQ[ Divisors[n] ], False] - 1, {n, 1, 105} ]`
	CROSSREFS	`Complement of A083399.` `A033273(n-1) - 1.` `Cf. A137944, A137945.` `Sequence in context: A147602 A114206 A073202 this_sequence A028422 A064577 A113949` `Adjacent sequences: A055209 A055210 A055211 this_sequence A055213 A055214 A055215`
	KEYWORD	`easy,nonn`
	AUTHOR	`Leroy Quet, Jun 23 2000`

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Last modified December 19 12:50 EST 2009. Contains 171053 sequences.

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