id:A056704 - OEIS Search Results

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

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1, 2, 5, 10, 11, 13, 34, 47, 52, 77, 88, 554, 580, 1310, 1505, 8537 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (28*10^n-1)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 311...11` `Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 3*10^n + (10^n-1)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Sequence in context: A140707 A136817 A140180 this_sequence A163624 A167799 A032874` `Adjacent sequences: A056701 A056702 A056703 this_sequence A056705 A056706 A056707`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 10 2000`

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