id:A056658 - OEIS Search Results

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Numbers n such that 60*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

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1, 2, 3, 9, 17, 20, 21, 27, 42, 65, 120, 132, 177, 240, 453, 552, 1599, 2174, 2977, 3648, 7707, 8315 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (2*10^(n+1)-17)/3 is prime.`
	LINKS	`Index entries for primes involving repunits` `Makoto Kamada, Factorizations of 66...661.`
	MATHEMATICA	`Do[ If[ PrimeQ[ 60*(10^n - 1)/9 + 1], Print[n]], {n, 7000}]`
	CROSSREFS	`Cf. A092571 (corresponding primes).` `Sequence in context: A086771 A156066 A143890 this_sequence A034467 A065965 A108827` `Adjacent sequences: A056655 A056656 A056657 this_sequence A056659 A056660 A056661`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 09 2000`
	EXTENSIONS	`1599 and 2174 (corresponding to probable primes) from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Feb 28 2004` `More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008`

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