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A083668
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Prime indices of prime Fibonacci numbers.
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8
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3, 5, 7, 11, 13, 17, 23, 29, 43, 47, 83, 131, 137, 359, 431, 433, 449, 509, 569, 571, 2971, 4723, 5387, 9311, 9677, 14431, 25561, 30757, 35999, 37511, 50833, 81839, 104911, 130021, 148091, 201107, 397379, 433781, 590041, 593689, 604711, 931517, 1049897, 1285607, 1636007, 1803059, 1968721
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OFFSET
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1,1
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COMMENTS
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Same as A001605 without the number 4.
Also the indices of prime Fibonacci numbers which can be written as the sum of two positive squares.
The Fibonacci numbers F(6k+1) and F(6k+5) are congruent to 1 (mod 4).
(End)
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LINKS
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EXAMPLE
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For Fib(n) to be prime, n must be prime, except for n=4. The first 9 primes are: 2, 3, 5, 7, 11, 13, 17, 19 and 23. The corresponding Fibonacci numbers are: 1, 2, 5, 13, 89, 233, 1597, 4181 and 28657. All of these are prime except Fib(2) = 1 and Fib(19) = 4181. So the first 7 terms of this sequence are 3, 5, 7, 11, 13, 17 and 23.
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MATHEMATICA
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Do[ If[ PrimeQ[ Fibonacci[ Prime[n]]], Print[ Prime[n]]], {n, 1, 1000}]
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PROG
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(PARI) pif(n) = { forprime(x=2, n, if(isprime(fibonacci(x)), print1(x" "))) }
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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Terms a(42) to a(47) added by V. Raman, Oct 04 2012
Definition and wrong statement in example corrected by M. F. Hasler, Oct 08 2012
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STATUS
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approved
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