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A092480
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Primes of the form 40*R_n + 7, where R_n is the repunit (A002275) of length n.
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2
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OFFSET
| 1,1
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COMMENTS
| Primes of the form ((4*10^n-31)/9)+6. - Vincenzo Librandi, Dec 13 2011
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..7
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MATHEMATICA
| Select[Table[(((4*10^n-31)/ 9)+6), {n, 1, 800}], PrimeQ] (* Vincenzo Librandi, Dec 13 2011 *)
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PROG
| (MAGMA) [a: n in [1..720] | IsPrime(a) where a is ((4*10^n-31) div 9)+6 ]; // Vincenzo Librandi, Dec 13 2011
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CROSSREFS
| Cf. A056682 (corresponding n).
Sequence in context: A013403 A013401 A020465 * A088143 A124880 A171312
Adjacent sequences: A092477 A092478 A092479 * A092481 A092482 A092483
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KEYWORD
| nonn
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AUTHOR
| Rick L. Shepherd (rshepherd2(AT)hotmail.com), Apr 03 2004
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