A099410 - OEIS

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A099410

Numbers n such that 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 3, 5, 14, 176, 416, 2505, 2759 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`Also numbers n such that (2*10^n+61)/9 is prime.`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 2(10^n - 1)/9 + 7], Print[n]], {n, 5000}]`
	CROSSREFS	`Sequence in context: A104870 A114411 A155698 * A102033 A174418 A072246` `Adjacent sequences: A099407 A099408 A099409 * A099411 A099412 A099413`
	KEYWORD	`nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2004`

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Last modified February 16 19:05 EST 2012. Contains 205943 sequences.