id:A083647 - OEIS Search Results

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For primes p: Number of steps to reach 2 when iterating f(p) = greatest prime divisor of p-1.

+0
3

0, 1, 1, 2, 2, 2, 1, 2, 3, 3, 2, 2, 2, 3, 4, 3, 4, 2, 3, 3, 2, 3, 3, 3, 2, 2, 2, 4, 2, 3, 3, 3, 2, 4, 3, 2, 3, 2, 4, 4, 4, 2, 3, 2, 3, 3, 3, 3, 4, 3, 4, 2, 2, 2, 1, 4, 4, 2, 4, 3, 5, 3, 2, 3, 3, 4, 3, 3, 5, 4, 3, 5, 3, 3, 3, 4, 3, 3, 2, 2, 3, 3, 4, 2, 3, 2, 3, 3, 4, 3, 5, 3, 2, 3, 4, 3, 4, 3, 4, 2, 3, 5, 4, 4, 3 (list; graph; listen)

	OFFSET	`1,4`
	COMMENT	`For smallest prime that requires n steps to reach 2 cf. A082449.`
	EXAMPLE	`59 is the 17th prime and takes four steps to reach 2 (59 -> 29 -> 7 ->3 -> 2), so a(17) = 4.`
	PROGRAM	`(PARI) {forprime(p=2, 571, q=p; c=0; while(q>2, fac=factor(q-1); q=fac[matsize(fac)[1], 1]; c++); print1(c, ", "))}`
	CROSSREFS	`Cf. A006530, A023503, A082449.` `Sequence in context: A120965 A006371 A000177 this_sequence A056691 A130790 A029330` `Adjacent sequences: A083644 A083645 A083646 this_sequence A083648 A083649 A083650`
	KEYWORD	`nonn`
	AUTHOR	`Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 01 2003`

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

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