id:A056695 - OEIS Search Results

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Numbers n such that 80*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

+0
3

0, 2, 3, 5, 8, 11, 71, 117, 123, 189, 243, 303, 356, 1421, 2690, 5537, 7580 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (8*10^(n+1)-17)/9 is prime.`
	LINKS	`Index entries for primes involving repunits` `Makoto Kamada, Factorizations of 88...887.`
	MATHEMATICA	`Do[ If[ PrimeQ[80*(10^n - 1)/9 + 7], Print[n]], {n, 0, 5000}]`
	CROSSREFS	`Sequence in context: A114831 A092362 A105766 this_sequence A020899 A057987 A067288` `Adjacent sequences: A056692 A056693 A056694 this_sequence A056696 A056697 A056698`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 10 2000`
	EXTENSIONS	`More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008`

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Last modified December 18 21:37 EST 2009. Contains 171024 sequences.