id:A056656 - OEIS Search Results

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Numbers n such that 20*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

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0, 1, 2, 7, 10, 35, 94, 100, 127, 259, 350, 466, 644, 1010, 1177, 1216, 2441, 3760, 3805 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`Also numbers n such that (2*10^(n+1)+7)/9 is prime.` `2441 produces a probable prime. - Rick L. Shepherd (rshepherd2(AT)hotmail.com), Mar 27 2004`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 20*(10^n - 1)/9 + 3 ], Print[n]], {n, 7000}]`
	CROSSREFS	`Cf. A093162 (corresponding primes).` `Sequence in context: A091295 A084184 A015963 this_sequence A151346 A110739 A133154` `Adjacent sequences: A056653 A056654 A056655 this_sequence A056657 A056658 A056659`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 09 2000`
	EXTENSIONS	`2441 from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Mar 27 2004`

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Last modified November 21 18:23 EST 2009. Contains 167309 sequences.