A103009 - OEIS

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A103009

Numbers n such that 5*10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 4, 7, 103, 166, 280, 475, 505, 835, 922, 2018, 4435, 4459, 7615, 8558, 17164, 22801 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (47*10^n+7)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 522...223.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(46*10^n + 7)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A082537 A004577 A076719 * A174393 A153662 A063864` `Adjacent sequences: A103006 A103007 A103008 * A103010 A103011 A103012`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 18 2005`
	EXTENSIONS	`a(17)-a(18) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 14 2010`

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Last modified February 14 08:58 EST 2012. Contains 205614 sequences.