id:A056715 - OEIS Search Results

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Numbers n such that 5*10^n + 7*R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.

+0
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0, 2, 8, 14, 17, 18, 33, 35, 126, 183, 324, 344, 866, 992, 1226, 2355 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (52*10^n-7)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 577...77` `Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 510^n + 7(10^n-1)/9], Print[n]], {n, 0, 5000}]`
	CROSSREFS	`Sequence in context: A066567 A002248 A050619 this_sequence A160556 A105610 A117104` `Adjacent sequences: A056712 A056713 A056714 this_sequence A056716 A056717 A056718`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 11 2000`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.