A099418 - OEIS

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A099418

Numbers n such that 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 8, 12, 18, 26, 32, 138, 188, 222, 338, 1002, 2744 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`Also numbers n such that (5*10^n+31)/9 is prime.`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 5(10^n - 1)/9 + 4], Print[n]], {n, 0, 5000}]`
	CROSSREFS	`Sequence in context: A090772 A046525 A057265 * A108987 A035405 A111058` `Adjacent sequences: A099415 A099416 A099417 * A099419 A099420 A099421`
	KEYWORD	`nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2004`

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Last modified February 17 05:54 EST 2012. Contains 205985 sequences.