id:A086766 - OEIS Search Results

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a(n) = smallest r where (concatenation of n, r times with itself)*10 +1 is a prime given by A087403(n), or 0 if no such number exists.

+0
3

1, 3, 1, 1, 11, 1, 1, 2, 2, 1, 9, 3, 1, 5, 1, 3, 15, 1, 1, 2, 1, 60, 3, 1, 1, 2, 1, 1, 5, 5, 1, 2, 1, 6, 12, 3, 12, 3, 5, 1, 2, 1, 1, 5, 3, 1, 0, 2, 1, 9, 2, 1, 6, 1, 6, 18, 1, 3, 45, 1, 6, 3, 1, 1, 2, 1, 0, 3, 1, 1, 2, 3, 4, 8, 1, 1, 6, 2, 36, 96, 1, 1, 5, 304, 6, 2, 6, 1, 2, 2, 1, 2, 5, 1, 6, 5, 1, 2, 1, 0 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Conjecture: No term is zero.` `a(47)=a(67)=a(100)=a(107)=a(114)=0 (r values tested up to 1000). - Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 23 2003`
	EXAMPLE	`a(2) =3, 2221 is a prime but 21, and 221 are composite.`
	CROSSREFS	`Cf. A087403.` `Sequence in context: A087647 A100265 A111473 this_sequence A078688 A082466 A120270` `Adjacent sequences: A086763 A086764 A086765 this_sequence A086767 A086768 A086769`
	KEYWORD	`base,nonn`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 10 2003`
	EXTENSIONS	`More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 23 2003`

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Last modified November 21 14:49 EST 2008. Contains 150807 sequences.

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