A103080 - OEIS

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A103080

Numbers n such that 8*10^n + 4*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 3, 4, 10, 15, 25, 69, 159, 166, 261, 442, 1339, 1797, 2170, 3163, 3472, 4917, 18267 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (76*10^n-13)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 844...443.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(76*10^n - 13)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A056517 A048155 A204292 * A055720 A054184 A188022` `Adjacent sequences: A103077 A103078 A103079 * A103081 A103082 A103083`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2005`
	EXTENSIONS	`a(18) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 14 2010`

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Last modified February 14 01:35 EST 2012. Contains 205567 sequences.