A099421 - OEIS

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A099421

Numbers n such that 8*R_n - 7 is a prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 3, 19, 79, 139, 223, 463, 544, 1096, 1419, 3247, 3877, 4417, 9507, 11091, 14602 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (8*10^n-71)/9 is a prime.`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 8(10^n - 1)/9 - 7], Print[n]], {n, 0, 15000}]`
	CROSSREFS	`Sequence in context: A202041 A027175 A093734 * A061171 A163431 A167242` `Adjacent sequences: A099418 A099419 A099420 * A099422 A099423 A099424`
	KEYWORD	`nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2004`

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Last modified February 13 14:31 EST 2012. Contains 205511 sequences.