A055768 - OEIS

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A055768

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

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; refs; listen; history; text; internal format)

	OFFSET	`1,4`
	LINKS	`Reinhard Zumkeller, Table of n, a(n) for n = 1..10000`
	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.`
	PROG	`(Haskell)` `a055768 = a001221 . a005867 -- Reinhard Zumkeller, May 01 2013`
	CROSSREFS	`Cf. A002110, A000010, A001221.` `Cf. A055769.` `Sequence in context: A194235 A029120 A078428 * A064952 A176001 A194272` `Adjacent sequences: A055765 A055766 A055767 * A055769 A055770 A055771`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), Jul 12 2000`
	STATUS	`approved`

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Last modified June 19 19:50 EDT 2013. Contains 226416 sequences.