A099413 - OEIS

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A099413

Numbers n such that 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 2, 4, 10, 20, 26, 722, 1310, 3170 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,3`
	COMMENTS	`Also numbers n such that (4*10^n+23)/9 is prime.`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 4(10^n - 1)/9 + 3], Print[n]], {n, 5000}]`
	CROSSREFS	`Sequence in context: A011963 A083844 A026554 * A174175 A127392 A189585` `Adjacent sequences: A099410 A099411 A099412 * A099414 A099415 A099416`
	KEYWORD	`nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2004`

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Last modified February 15 15:20 EST 2012. Contains 205823 sequences.