A102988 - OEIS

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A102988

Numbers n such that 4*10^n + 3*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 4, 7, 10, 12, 20, 24, 30, 42, 62, 188, 304, 340, 715, 804, 1040, 1887, 2079, 2120, 2260, 2423, 3319, 5598, 6072, 22048, 25713, 28644 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (13*10^n-7)/3 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 433...331.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(13*10^n - 7)/3], Print[n]], {n, 1, 10000}]`
	CROSSREFS	`Sequence in context: A007087 A101359 A007303 * A080137 A102933 A122019` `Adjacent sequences: A102985 A102986 A102987 * A102989 A102990 A102991`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 17 2005`
	EXTENSIONS	`Addition of a(26)-a(28) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 08 2010`

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Last modified February 15 03:22 EST 2012. Contains 205694 sequences.