A102980 - OEIS

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A102980

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.

2, 3, 6, 17, 20, 45, 57, 78, 119, 137, 509, 710, 1127, 1518, 1761, 3086, 3147, 9926, 19854, 27842, 46799, 49682, 68718, 100542, 106649, 191073 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`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: A103593 A174118 A006449 * A181185 A018284 A204514` `Adjacent sequences: A102977 A102978 A102979 * A102981 A102982 A102983`
	KEYWORD	`more,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 21 2004`
	EXTENSIONS	`Addition of a(19)-a(26) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 08 2010`

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Last modified February 14 23:04 EST 2012. Contains 205686 sequences.