id:A102957 - OEIS Search Results

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Numbers n such that 2*10^n + 6*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

+0
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1, 2, 4, 7, 14, 20, 39, 102, 156, 457, 1190, 2308, 5870, 8314, 9703 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (8*10^n+7)/3 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 266...669.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(8*10^n + 7)/3], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A108329 A057264 A045514 this_sequence A018567 A034426 A000075` `Adjacent sequences: A102954 A102955 A102956 this_sequence A102958 A102959 A102960`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 17 2004`

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.