id:A102991 - OEIS Search Results

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Numbers n such that 4*10^n + 5*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

+0
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1, 4, 7, 19, 34, 54, 78, 90, 213, 307, 702, 1456, 2139, 2214, 3066, 9300 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (41*10^n-23)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 455...553.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(41*10^n - 23)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A063605 A024824 A006381 this_sequence A062306 A140167 A006130` `Adjacent sequences: A102988 A102989 A102990 this_sequence A102992 A102993 A102994`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 17 2005`

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Last modified July 24 12:00 EDT 2008. Contains 142294 sequences.