id:A102953 - OEIS Search Results

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

+0
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1, 4, 7, 12, 30, 94, 178, 196, 564, 1801, 3520, 3538, 8233 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (22*10^n-13)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 244...443.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(22*10^n - 13)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A010901 A023624 A123194 this_sequence A111157 A162957 A051456` `Adjacent sequences: A102950 A102951 A102952 this_sequence A102954 A102955 A102956`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 17 2004`

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Last modified November 21 21:21 EST 2009. Contains 167310 sequences.