id:A103060 - OEIS Search Results

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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.

+0
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1, 2, 5, 7, 23, 32, 38, 47, 116, 140, 229, 247, 734, 931, 1346, 2162, 2546, 6980 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`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: A160820 A158357 A072953 this_sequence A103807 A099228 A106018` `Adjacent sequences: A103057 A103058 A103059 this_sequence A103061 A103062 A103063`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2005`

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Last modified December 7 23:50 EST 2009. Contains 170430 sequences.