id:A103009 - OEIS Search Results

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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.

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1, 2, 4, 7, 103, 166, 280, 475, 505, 835, 922, 2018, 4435, 4459, 7615, 8558 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`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 this_sequence A153662 A063864 A119927` `Adjacent sequences: A103006 A103007 A103008 this_sequence A103010 A103011 A103012`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 18 2005`

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Last modified November 21 21:21 EST 2009. Contains 167310 sequences.