id:A102980 - OEIS Search Results

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Numbers n such that 3*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

+0
2

2, 3, 6, 17, 20, 45, 57, 78, 119, 137, 509, 710, 1127, 1518, 1761, 3086, 3147, 9926 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Also numbers n such that (35*10^n+1)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 388...889.` `Index entries for primes involving repunits.`
	MATHEMATICA	`Do[ If[ PrimeQ[(35*10^n + 1)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A087983 A103593 A006449 this_sequence A018284 A078344 A024498` `Adjacent sequences: A102977 A102978 A102979 this_sequence A102981 A102982 A102983`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 21 2004`

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