id:A056727 - OEIS Search Results

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Numbers n such that 9*10^n + 7*R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.

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1, 2, 4, 19, 28, 73, 203, 220, 274, 292, 470, 763, 1891, 3307, 7007, 7306, 9755 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Also numbers n such that (88*10^n-7)/9 is prime.`
	LINKS	`Makoto Kamada, Factorizations of 977...77` `Index entries for primes involving repunits`
	MATHEMATICA	`Do[ If[ PrimeQ[ 910^n + 7(10^n-1)/9], Print[n]], {n, 0, 10000}]`
	CROSSREFS	`Cf. A093944 (corresponding primes).` `Sequence in context: A009508 A009418 A153691 this_sequence A154140 A131578 A018273` `Adjacent sequences: A056724 A056725 A056726 this_sequence A056728 A056729 A056730`
	KEYWORD	`hard,nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 11 2000`

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Last modified November 21 21:21 EST 2009. Contains 167310 sequences.