id:A074727 - 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 + SOD(n) + 1, otherwise 2n - SOD(n) - 1, where SOD(n) is the sum of the digits of n; or -1 if no prime is ever reached.

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1, 1, 1, 2, 1, 2, 6, 7, 4, 1, 2, 4, 16, 1, 6, 6, 2, 3, 1, 3, 3, 6, 3, 5, 1, 2, 1, 2, 2, 2, 15, 1, 15, 1, 7, 3, 2, 21, 5, 15, 4, 16, 1, 8, 1, 7, 1, 2, 7, 7, 2, 1, 20, 2, 15, 1, 6, 1, 1, 8, 22, 2, 1, 20, 64, 3, 1, 31, 14, 22, 19, 66, 7, 1, 14, 1, 15, 10, 7, 2, 6, 19, 1, 4, 8, 2, 1, 7, 18, 3, 2, 1, 2 (list; graph; listen)

	OFFSET	`2,4`
	EXAMPLE	`a(10) = 4 because 10 -> 22 -> 49 -> 84 -> 181.`
	CROSSREFS	`Sequence in context: A094965 A025277 A153896 this_sequence A059587 A070236 A020825` `Adjacent sequences: A074724 A074725 A074726 this_sequence A074728 A074729 A074730`
	KEYWORD	`nonn`
	AUTHOR	`Jason Earls (zevi_35711(AT)yahoo.com), Sep 04 2002`

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Last modified November 30 13:13 EST 2009. Contains 167758 sequences.

AT&T Labs Research