id:A065854 - OEIS Search Results

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Smallest prime q such that (p^q-1)/(p-1) is a prime, where p = prime(n).

+0
6

2, 3, 3, 5, 17, 5, 3, 19, 5, 5, 7, 13, 3, 5, 127, 11, 3, 7, 19, 3, 5, 5, 5, 3, 17, 3, 19, 17, 17, 23, 5, 3, 11, 163, 7, 13, 17, 7, 3, 3, 19, 17, 17, 5, 31, 577, 41, 239, 5, 11, 113, 5, 17, 7, 23, 5 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`a(n) = 2*A065813(n)+1, n > 1.`
	LINKS	`Andy Steward, Titanic Prime Generalized Repunits`
	MATHEMATICA	`Do[p = Prime[n]; k = 1; While[ !PrimeQ[ (p^Prime[k] - 1)/(p - 1)], k++ ]; Print[ Prime[k]], {n, 1, 56} ]`
	CROSSREFS	`Cf. A084740 (least k such that (n^k-1)/(n-1) is prime).` `Sequence in context: A064339 A053199 A045626 this_sequence A064776 A096659 A046826` `Adjacent sequences: A065851 A065852 A065853 this_sequence A065855 A065856 A065857`
	KEYWORD	`hard,nonn`
	AUTHOR	`Vladeta Jovovic (vladeta(AT)Eunet.yu), Nov 26 2001`

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.

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