id:A103054 - OEIS Search Results

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Numbers n such that 7*10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

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1, 3, 4, 7, 9, 13, 33, 37, 76, 147, 297, 1851, 3457, 3609 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (65*10^n+61)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 722...229.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(65*10^n + 61)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A004652 A061568 A146994 this_sequence A140208 A098390 A008763` `Adjacent sequences: A103051 A103052 A103053 this_sequence A103055 A103056 A103057`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2005`

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Last modified February 9 11:24 EST 2010. Contains 172296 sequences.