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A183178
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Numbers n such that (7*10^(2n+1)-45*10^n-7)/9 is prime.
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1
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OFFSET
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1,2
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REFERENCES
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C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
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LINKS
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Table of n, a(n) for n=1..10.
Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)
Makoto Kamada, Prime numbers of the form 77...77277...77
Index entries for primes involving repunits.
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FORMULA
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a(n) = (A077777(n)-1)/2.
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MATHEMATICA
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Do[If[PrimeQ[(7*10^(2n + 1) - 45*10^n - 7)/9], Print[n]], {n, 3000}]
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CROSSREFS
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Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
Sequence in context: A013574 A020679 A103541 * A145004 A226723 A029918
Adjacent sequences: A183175 A183176 A183177 * A183179 A183180 A183181
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KEYWORD
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nonn
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AUTHOR
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Ray Chandler, Dec 28 2010
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STATUS
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approved
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