A056680 - OEIS

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A056680

Numbers n such that 30*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 2, 5, 45, 393, 977, 2585, 2810, 2967, 3641, 4826, 4917, 5591, 5705 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,3`
	COMMENTS	`Also numbers n such that (10^(n+1)+11)/3 is prime.`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[30*(10^n - 1)/9 + 7], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A027730 A163115 A088309 * A005166 A121621 A119715` `Adjacent sequences: A056677 A056678 A056679 * A056681 A056682 A056683`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 10 2000`

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Last modified February 17 19:13 EST 2012. Contains 206085 sequences.