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A108837
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Primes of the form 5*10^n-7.
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2
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OFFSET
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1,1
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COMMENTS
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Primes such that the leftmost digit is 4, the rightmost digit is 3, and all inner digits are 9.
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LINKS
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FORMULA
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MATHEMATICA
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Select[Table[FromDigits[Join[PadRight[{4}, n+1, 9], {3}]], {n, 0, 150}], PrimeQ] (* Harvey P. Dale, Feb 01 2012 *)
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PROG
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(PARI) n10np9(n, d) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+(10^x-1)*10+k-1; if(isprime(y), print1(y", ")) ) ) }
(Magma)[a: n in [1..250]|IsPrime(a) where a is (5*10^n-7)] // Vincenzo Librandi, Dec 11 2010
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CROSSREFS
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KEYWORD
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easy,nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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