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A216552
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Numbers n such that the n-th Fibonacci number is prime and can be written in the form a^2 + 3*b^2.
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1
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4, 7, 17, 23, 47, 137, 359, 431, 433, 449, 569, 9311, 14431, 25561, 35999, 37511, 50833, 81839, 104911, 590041, 593689, 604711, 1049897, 1285607, 1636007, 1968721
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OFFSET
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1,1
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COMMENTS
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Primes are of the form a^2 + 3*b^2 if and only if they are not of the form 3k + 2 (cf. A003136), and Fibonacci(n) = 2 (mod 3) if and only if n is in A047443 (i.e., n = 3, 5 or 6 (mod 8)), so the second condition can be considerably simplified. - M. F. Hasler, Sep 29 2012
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LINKS
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FORMULA
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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