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Search: id:A050937
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| A050937 |
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Composite Fibonacci numbers with a prime index. |
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+0
22
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| 1, 4181, 1346269, 24157817, 165580141, 53316291173, 956722026041, 2504730781961, 44945570212853, 308061521170129, 806515533049393, 14472334024676221, 1779979416004714189, 83621143489848422977
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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David Wells, The Penguin Dictionary of Curious and Interesting Numbers, entry 4181.
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EXAMPLE
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Fibonacci(19) = 4181 is a composite Fibonacci number, but its index 19 is prime.
Fibonacci(2) = 1 is a nonprime with a prime index, so is Fibonacci(19) = 4181 = 37*113.
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MAPLE
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for n from 1 to 200 do if isprime(n) and (not isprime( fibonacci(n))) then print( fibonacci(n)): fi: od:
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PROGRAM
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(PARI) f(n) = forprime(x=2, n, p=fibonacci(x); if(!isprime(p), print1(p", ")))- Cino Hilliard (hillcino368(AT)gmail.com), Feb 11 2004
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CROSSREFS
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A038672 gives the indices.
Sequence in context: A072322 A045728 A048593 this_sequence A135953 A152511 A103614
Adjacent sequences: A050934 A050935 A050936 this_sequence A050938 A050939 A050940
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KEYWORD
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nonn
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AUTHOR
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Jud McCranie (j.mccranie(AT)comcast.net), Jan 01 2000
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