id:A103015 - OEIS Search Results

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Numbers n such that 5*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

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2, 6, 8, 18, 53, 68, 242, 276, 320, 564, 620, 1782, 2340, 2454, 5765 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Also numbers n such that (49*10^n+23)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 544...447.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(49*10^n + 23)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A102656 A163911 A077638 this_sequence A098092 A106164 A072230` `Adjacent sequences: A103012 A103013 A103014 this_sequence A103016 A103017 A103018`
	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.