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Search: id:A071683
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| A071683 |
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Nonprimes which are the average of two consecutive Fibonacci numbers. |
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+0
1
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| 1, 4, 72, 305, 1292, 5473, 23184, 98209, 416020, 1762289, 7465176, 31622993, 133957148, 567451585, 2403763488, 10182505537, 43133785636, 182717648081, 774004377960, 3278735159921, 13888945017644, 58834515230497
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OFFSET
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1,2
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COMMENT
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Prove that 17 is the only prime which is the average of two consecutive Fibonacci numbers.
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MATHEMATICA
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f[n_] := Fibonacci[n]; a = Select[ Range[70], IntegerQ[(f[ # ] + f[ # + 1])/2] && !PrimeQ[(f[ # ] + f[ # + 1])/2] &]; (f[a] + f[a + 1])/2
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CROSSREFS
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Cf. A018252, A000045.
Sequence in context: A113839 A077112 A095385 this_sequence A003752 A062018 A119580
Adjacent sequences: A071680 A071681 A071682 this_sequence A071684 A071685 A071686
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KEYWORD
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nonn
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AUTHOR
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G. L. Honaker, Jr. (honak3r(AT)gmail.com), Jun 22 2002
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EXTENSIONS
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Edited by Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 27 2002
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