A056683 - OEIS

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A056683

Numbers n such that 40*R_n + 9 is prime, where R_n = 11...1 is the repunit (A002275).

2, 4, 5, 47, 107, 244, 1043 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,1`
	COMMENTS	`Also numbers n such that (4*10^(n+1)+41)/9 is prime.`
	LINKS	`Table of n, a(n) for n=1..7.` `Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[40*(10^n - 1)/9 + 9], Print[n]], {n, 5000}]`
	CROSSREFS	`Sequence in context: A154775 A210418 A167454 * A105288 A066684 A128124` `Adjacent sequences: A056680 A056681 A056682 * A056684 A056685 A056686`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v, Aug 10 2000`
	STATUS	`approved`

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Last modified June 19 16:15 EDT 2013. Contains 226414 sequences.