id:A074807 - OEIS Search Results

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Number of steps needed to reach a prime when the following map is repeatedly applied to n: if n is even then 2n + POD(n) + 1, otherwise 2n - POD(n) - 1, where POD(n) is the product of the digits of n; or -1 if no prime is ever reached.

+0
1

2, 1, 1, 1, 2, 1, 2, 4, 5, 4, 2, 4, 3, 5, 5, 3, 5, 3, 2, 1, 3, 2, 3, 4, 3, 4, 3, 1, 3, 1, 2, 1, 4, 6, 3, 3, 5, 1, 2, 6, 6, 5, 1, 5, 2, 4, 4, 2, 1, 1, 8, 4, 2, 2, 3, 3, 3, 1, 6, 2, 4, 1, 1, 5, 3, 2, 3, 6, 1, 2, 2, 5, 2, 4, 2, 5, 5, 2, 5, 13, 5, 1, 2, 2, 2, 7, 4, 1, 5, 1, 2, 3, 4, 4, 4, 7, 3, 1, 2, 2, 2, 2, 2, 4 (list; graph; listen)

	OFFSET	`1,1`
	EXAMPLE	`a(8) = 4 because 8 -> 25 -> 39 -> 50 -> 101.`
	CROSSREFS	`Sequence in context: A097637 A161094 A002339 this_sequence A165194 A002951 A093993` `Adjacent sequences: A074804 A074805 A074806 this_sequence A074808 A074809 A074810`
	KEYWORD	`base,nonn`
	AUTHOR	`Jason Earls (zevi_35711(AT)yahoo.com), Sep 08 2002`

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Last modified December 16 13:01 EST 2009. Contains 170825 sequences.

AT&T Labs Research