id:A056707 - OEIS Search Results

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Numbers n such that 4*10^n + 3*R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.

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1, 2, 16, 31, 37, 55, 62, 172, 174, 197, 727, 1246, 1752, 4318, 4328, 4930, 6450 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (13*10^n-1)/3 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 433...33` `Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 410^n + 3(10^n-1)/9], Print[n]], {n, 0, 5000}]`
	CROSSREFS	`Sequence in context: A113933 A127871 A109210 this_sequence A069256 A120069 A018975` `Adjacent sequences: A056704 A056705 A056706 this_sequence A056708 A056709 A056710`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 10 2000`
	EXTENSIONS	`26044 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008`

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Last modified November 27 22:38 EST 2009. Contains 167602 sequences.