A056685 - OEIS

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A056685

Numbers n such that 50*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 7, 25, 65, 73, 232, 472, 539, 2773 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,3`
	COMMENTS	`Also numbers n such that (5*10^(n+1)-23)/9 is prime.`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[50*(10^n - 1)/9 + 3], Print[n]], {n, 0, 5000}]`
	CROSSREFS	`Sequence in context: A127765 A155305 A155290 * A001296 A000970 A155245` `Adjacent sequences: A056682 A056683 A056684 * A056686 A056687 A056688`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 10 2000`

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Last modified February 15 21:56 EST 2012. Contains 205860 sequences.