id:A103008 - 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.

+0
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2, 9, 12, 15, 26, 45, 62, 80, 128, 326, 494, 614, 710, 1641, 1646, 2103, 8514, 8688 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Also numbers n such that (47*10^n-11)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 522...221.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(47*10^n - 11)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A030376 A080520 A032372 this_sequence A124742 A152003 A050855` `Adjacent sequences: A103005 A103006 A103007 this_sequence A103009 A103010 A103011`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 18 2005`

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Last modified February 9 11:24 EST 2010. Contains 172296 sequences.