id:A103063 - OEIS Search Results

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Numbers n such that 7*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

+0
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1, 2, 6, 25, 69, 253, 300, 384, 434, 721, 822, 883, 2192, 2649, 3441, 3445, 8028 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (23*10^n-17)/3 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 766...661.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(23*10^n - 17)/3], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A123150 A086591 A073545 this_sequence A030228 A066317 A027104` `Adjacent sequences: A103060 A103061 A103062 this_sequence A103064 A103065 A103066`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2005`

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Last modified December 10 00:48 EST 2009. Contains 170565 sequences.