A093017 - OEIS

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A093017

Luhn algorithm double-and-add sum of digits of n.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 7, 8, 9, 10, 11, 12, 13 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	COMMENTS	`Starting on the right, sum digits after doubling alternating digits beginning with the second. If doubled digit >9, reduce by 9 (sum of digits).`
	LINKS	`John Kilgo, DotNetJohn.com, Using the Luhn Algorithm` `Webopedia, Luhn formula`
	EXAMPLE	`a(18) = 21 + 8 = 10.` `a(59) = (1+0) + 9 = 10 (1 and 0 are the digits in 10 = 25).`
	CROSSREFS	`Cf. A093018-A093029.` `Sequence in context: A177895 A189506 A173529 * A028897 A156230 A081594` `Adjacent sequences: A093014 A093015 A093016 * A093018 A093019 A093020`
	KEYWORD	`easy,nonn,base`
	AUTHOR	`Ray Chandler (rayjchandler(AT)sbcglobal.net), Apr 3 2004`

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Last modified February 15 15:20 EST 2012. Contains 205823 sequences.