A102993 - OEIS

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A102993

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

6, 21, 22, 24, 51, 81, 132, 165, 621, 1450, 3424, 5979, 11526, 26980 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`Also numbers n such that (41*10^n+31)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 455...559.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(41*10^n + 31)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A064929 A200831 A184291 * A143416 A164698 A020880` `Adjacent sequences: A102990 A102991 A102992 * A102994 A102995 A102996`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 17 2005`
	EXTENSIONS	`Addition of a(13)-a(14) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 12 2010`

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Last modified February 16 17:11 EST 2012. Contains 205938 sequences.