A056705 - OEIS

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A056705

Numbers n such that 3*10^n + 7*R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 11, 17, 773, 18155 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,3`
	COMMENTS	`Also numbers n such that (34*10^n-7)/9 is prime.`
	LINKS	`Table of n, a(n) for n=1..6.` `Makoto Kamada, Factorizations of 377...77` `Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 310^n + 7(10^n-1)/9], Print[n]], {n, 0, 30070}]`
	CROSSREFS	`Sequence in context: A166655 A146446 A132092 * A065706 A078874 A162555` `Adjacent sequences: A056702 A056703 A056704 * A056706 A056707 A056708`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v, Aug 10 2000`
	STATUS	`approved`

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Last modified May 22 18:04 EDT 2013. Contains 225560 sequences.