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A101396
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Numbers n such that 4*10^n - 9 is prime.
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1
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1, 17, 19, 29, 43, 119, 173, 949, 1609, 5579, 19679, 34147, 43493, 97799
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OFFSET
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1,2
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COMMENTS
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All terms are odd, since 4 * 10^(2*k) - 9 = (2 * 10^k - 3)*(2 * 10^k + 3). - Robert Israel, Mar 17 2015
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LINKS
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FORMULA
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EXAMPLE
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n = 1, 17, 19 are members since 31, 399999999999999991 and 39999999999999999991 are primes.
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MAPLE
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select(n -> n::odd and isprime(4*10^n-9), [$1..10000]); # Robert Israel, Mar 17 2015
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MATHEMATICA
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Do[ If[ PrimeQ[4*10^n - 9], Print[n]], {n, 0, 10000}]
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PROG
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
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EXTENSIONS
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a(11) from Kamada link by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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STATUS
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approved
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