A103060 - OEIS

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A103060

Numbers n such that 7*10^n + 5*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 5, 7, 23, 32, 38, 47, 116, 140, 229, 247, 734, 931, 1346, 2162, 2546, 6980, 10283, 10543, 12128, 13741 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Also numbers n such that (68*10^n-41)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 755...551.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(68*10^n - 41)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A158357 A072953 A175552 * A103807 A099228 A106018` `Adjacent sequences: A103057 A103058 A103059 * A103061 A103062 A103063`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2005`
	EXTENSIONS	`a(19)-a(22) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 14 2010`

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Last modified February 13 19:52 EST 2012. Contains 205536 sequences.