id:A102985 - OEIS Search Results

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

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0, 1, 4, 9, 10, 31, 70, 160, 171, 277, 630, 724, 3717, 5542, 5634 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`Also numbers n such that (38*10^n+7)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 422...223.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(38*10^n + 7)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A113434 A141395 A121215 this_sequence A112401 A115688 A115710` `Adjacent sequences: A102982 A102983 A102984 this_sequence A102986 A102987 A102988`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 17 2005`

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Last modified November 29 12:46 EST 2009. Contains 167659 sequences.