id:A055768 - OEIS Search Results

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Number of distinct primes dividing EulerPhi of n-th primorial number.

+0
2

0, 1, 1, 2, 3, 3, 3, 3, 4, 5, 5, 5, 5, 5, 6, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 10, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 13, 14, 15, 15, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 18, 19, 19, 19, 19, 20, 21, 21, 22, 22, 23, 23, 23, 24, 24, 24, 25, 26, 26, 26, 27, 28, 28 (list; graph; listen)

	OFFSET	`1,4`
	FORMULA	`a(n)=A001221[A000010[A002110(n)]]]=A001221[A005867(n)]`
	EXAMPLE	`When primorials have 10, 100, 1000 prime factors, then their EulerPhi has only 5, 32 or 241 prime divisors.`
	CROSSREFS	`Cf. A002110, A000010, A001221.` `Sequence in context: A130822 A029120 A078428 this_sequence A064952 A025776 A120505` `Adjacent sequences: A055765 A055766 A055767 this_sequence A055769 A055770 A055771`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), Jul 12 2000`

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Last modified September 6 16:04 EDT 2008. Contains 143483 sequences.

AT&T Labs Research