A102931 - OEIS

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A102931

Numbers n such that 10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 3, 6, 51, 57, 63, 150, 393, 420, 547 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (11*10^n+61)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 122...229.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(11*10^n + 61)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A032322 A203765 A111752 * A056447 A056437 A012275` `Adjacent sequences: A102928 A102929 A102930 * A102932 A102933 A102934`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 16 2004`

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Last modified February 17 14:50 EST 2012. Contains 206050 sequences.