A096845 - OEIS

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A096845

Numbers n for which 4*R_n - 1 is a prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 3, 6, 9, 12, 30, 32, 183, 297, 492 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (4*10^n-13)/9 is prime.`
	LINKS	`Index entries for primes involving repunits`
	EXAMPLE	`n=30 means that 444444444444444444444444444443 is prime.`
	MATHEMATICA	`Do[ If[ PrimeQ[ 4(10^n - 1)/9 - 1], Print[n]], {n, 5000}] (from Robert G. Wilson v Oct 14 2004)`
	CROSSREFS	`Cf. A096503-A096508, A096841-A096846, A000203.` `Sequence in context: A144677 A058616 A123316 * A190772 A130673 A062891` `Adjacent sequences: A096842 A096843 A096844 * A096846 A096847 A096848`
	KEYWORD	`hard,more,nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), Jul 15 2004`

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Last modified February 17 12:38 EST 2012. Contains 206021 sequences.