id:A061309 - OEIS Search Results

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a(n) is the smallest number required to make the concatenation of a(n) and 2n+1 a prime, or -1 if no such number exists.

+0
1

1, 0, 0, 0, 1, 0, 0, -1, 0, 0, 4, 0, -1, 1, 0, 0, 2, -1, 0, 1, 0, 0, -1, 0, 1, 1, 0, -1, 1, 0, 0, 1, -1, 0, 2, 0, 0, -1, 2, 0, 1, 0, -1, 4, 0, 1, 1, -1, 0, 1, 0, 0, -1, 0, 0, 2, 0, -1, 1, 3, 3, 1, -1, 0, 1, 0, 4, -1, 0, 0, 2, 2, -1, 5, 0, 0, 1, -1, 0, 4, 2, 0, -1, 0, 3, 1, 0, -1, 4, 0, 0, 13 (list; graph; listen)

	OFFSET	`0,11`
	COMMENT	`a(0) = 0 for a prime.`
	EXAMPLE	`a(9) = 0 as 19 itself is a prime; a(10) = 4 as 421 is a prime but 121, 221, 321 are not.`
	CROSSREFS	`Sequence in context: A117436 A068346 A006838 this_sequence A059064 A096459 A126222` `Adjacent sequences: A061306 A061307 A061308 this_sequence A061310 A061311 A061312`
	KEYWORD	`sign,base`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 26 2001`
	EXTENSIONS	`More terms from Frank.Ellermann(AT)t-online.de, Jun 15 2001`

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Last modified September 5 01:44 EDT 2008. Contains 143476 sequences.

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