id:A088276 - OEIS Search Results

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Smallest k such that 10^k + r is a prime ending (least significant digits) in r where r is the n-th odd number not divisible by 5. 0 if no such number exists.

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1, 1, 1, 1, 0, 2, 0, 3, 3, 0, 2, 0, 2, 3, 2, 2, 0, 5, 0, 2, 2, 0, 2, 0, 3, 2, 2, 3, 0, 2, 0, 2, 2, 0, 3, 0, 2, 2, 2, 2, 0, 3, 0, 3, 4, 0, 3, 0, 6, 3, 8, 3, 0, 4, 0, 4, 4, 0, 10, 0, 3, 3, 23, 4, 0, 3, 0, 4, 3, 0, 4, 0, 3, 5, 3, 5, 0, 3, 0, 6, 3, 0, 5, 0, 4, 3, 3, 633, 0, 3, 0, 3, 3, 0, 3, 0, 9, 4, 4, 3, 0, 4, 0 (list; graph; listen)

	OFFSET	`0,6`
	COMMENT	`Conjecture: (1) The only zero entries are for values of r == 2 (mod 3). (2) There are infinitely many values of k such that 10^k + r is a prime if r is not == 2 (mod 3).`
	EXAMPLE	`The term corresponding to 21 is 3 as 21, 121 both are composite and 1021 is a prime. 1021 = 10^3 + 21 hence k = 3.`
	CROSSREFS	`Sequence in context: A049799 A087985 A004557 this_sequence A099838 A127449 A138057` `Adjacent sequences: A088273 A088274 A088275 this_sequence A088277 A088278 A088279`
	KEYWORD	`base,nonn`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 28 2003`
	EXTENSIONS	`More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Oct 15 2003`

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Last modified July 26 13:41 EDT 2008. Contains 142293 sequences.

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