A056715 - OEIS

This site is supported by donations to The OEIS Foundation.

A056715

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, 2, 8, 14, 17, 18, 33, 35, 126, 183, 324, 344, 866, 992, 1226, 2355 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (52*10^n-7)/9 is prime.`
	LINKS	`Table of n, a(n) for n=1..16.` `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: A002248 A194278 A050619 * A160556 A105610 A117104` `Adjacent sequences: A056712 A056713 A056714 * A056716 A056717 A056718`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v, Aug 11 2000`
	STATUS	`approved`

Content is available under The OEIS End-User License Agreement .

Last modified May 25 19:30 EDT 2013. Contains 225649 sequences.