A056661 - OEIS

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A056661

Numbers n such that 40*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 2, 5, 8, 11, 29, 31, 182, 296, 491 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,3`
	COMMENTS	`Also numbers n such that (4*10^(n+1)-13)/9 is prime.`
	LINKS	`Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 40*(10^n - 1)/9 + 3], Print[n]], {n, 0, 5000}]`
	CROSSREFS	`Sequence in context: A129300 A107679 A018846 * A135050 A004112 A024815` `Adjacent sequences: A056658 A056659 A056660 * A056662 A056663 A056664`
	KEYWORD	`hard,more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 09 2000`

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Last modified February 17 08:44 EST 2012. Contains 205998 sequences.