A102938 - OEIS

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A102938

Numbers n such that 10^n + 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 3, 4, 7, 12, 51, 87, 123, 198, 202, 537, 831, 1323, 2508, 2631, 5568, 6897, 7524, 9939, 10674, 11617, 13257, 14371, 20176 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (14*10^n+31)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 155...559.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(14*10^n + 31)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A049859 A124636 A049930 * A076784 A088764 A093124` `Adjacent sequences: A102935 A102936 A102937 * A102939 A102940 A102941`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 16 2004`
	EXTENSIONS	`Addition of a(20)-a(24) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 08 2010`

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Last modified February 16 17:48 EST 2012. Contains 205939 sequences.