id:A103016 - OEIS Search Results

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

+0
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1, 3, 4, 6, 10, 21, 30, 72, 199, 208, 270, 396, 619, 759, 1077, 1383, 1566, 1960, 2653, 3504, 3786, 6085 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (49*10^n+41)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 544...449.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(49*10^n + 41)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A018908 A052548 A103049 this_sequence A061032 A091424 A092839` `Adjacent sequences: A103013 A103014 A103015 this_sequence A103017 A103018 A103019`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 18 2005`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.