A097685 - OEIS

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A097685

Numbers n such that R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 5, 6, 8, 17, 50, 684, 720, 1452, 1679, 3146 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`Also numbers n such that (10^n+71)/9 is prime.` `Values indicate primes of the form "(n-1) ones followed by a nine". Related to the base 10 repunit primes.`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[(10^n - 1)/9 + 8], Print[n]], {n, 0, 5000}] (from Robert G. Wilson v Oct 14 2004)`
	CROSSREFS	`Equals A056659 + 1. Cf. A004023, A097683, A097684.` `Sequence in context: A079256 A191204 A191140 * A136369 A007573 A143909` `Adjacent sequences: A097682 A097683 A097684 * A097686 A097687 A097688`
	KEYWORD	`nonn`
	AUTHOR	`Carl R. White (cyrek(AT)cyreksoft.yorks.com), Aug 19 2004`

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