id:A086920 - OEIS Search Results

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Smallest k such that n times concatenation of k with itself followed by a 1 is a prime, or 0 if no such number exists.

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8

1, 3, 2, 3, 3, 3, 3, 30, 6, 4, 5, 5, 25, 42, 17, 19, 2, 1, 7, 6, 6, 1, 50, 29, 138, 153, 4, 45, 54, 7, 15, 9, 78, 147, 95, 58, 102, 18, 3, 115, 54, 6, 46, 9, 24, 64, 183, 120, 3, 33, 112, 46, 105, 4, 279, 122, 68, 75, 3, 22, 294, 56, 92, 76, 6, 19, 94, 71, 12, 75, 30, 16, 78, 320, 33 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Conjecture: no term is zero.`
	EXAMPLE	`a(3) = 2 as 2221 is a prime. a(4) = 3 as 33331 is a prime but 11111 and 22221 are not.` `a(8) = 30 and the prime arising is 30303030303030301.`
	CROSSREFS	`Cf. A087604, A087605, A087606, A087607, A087608, A087609.` `Cf. A086923.` `Cf. A086766.` `Sequence in context: A079790 A098726 A065801 this_sequence A117451 A130970 A144733` `Adjacent sequences: A086917 A086918 A086919 this_sequence A086921 A086922 A086923`
	KEYWORD	`base,nonn`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 18 2003`
	EXTENSIONS	`More terms from Ray G. Opao (1260(AT)email.com), Apr 15 2004` `More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Apr 12 2005`

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Last modified December 17 19:39 EST 2009. Contains 170821 sequences.

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