id:A089147 - OEIS Search Results

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

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1, 3, 9, 13, 42, 51, 54, 91, 120, 168, 510, 819, 1071, 1756, 3010, 4333, 9534 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (16*10^n-7)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 177...77` `Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[10^n + 7(10^n - 1)/9], Print[ n]], {n, 7000}]`
	CROSSREFS	`For the primes see A088465.` `Sequence in context: A018407 A068885 A018292 this_sequence A094043 A134190 A047905` `Adjacent sequences: A089144 A089145 A089146 this_sequence A089148 A089149 A089150`
	KEYWORD	`base,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 05 2003`
	EXTENSIONS	`More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008`

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Last modified November 21 15:14 EST 2009. Contains 167308 sequences.