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A039595
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Fibonacci numbers that are also triangular numbers.
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5
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OFFSET
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1,2
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COMMENTS
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Vern Hoggatt conjectured and Luo Ming confirmed that these are all the terms. - Tomohiro Yamada, Sep 23 2017
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REFERENCES
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J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 55, p. 20, Ellipses, Paris 2008.
D. Wells, Curious and interesting numbers, Penguin Books, p. 108
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LINKS
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Table of n, a(n) for n=1..4.
Luo Ming, On triangular Fibonacci numbers, Fibonacci Quart. 27 (1989), 98--108.
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MATHEMATICA
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Union[Select[Fibonacci[Range[20]], OddQ[Sqrt[8#+1]]&]] (* Harvey P. Dale, Jan 17 2015 *)
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CROSSREFS
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Cf. A000045, A000217.
Sequence in context: A303834 A340687 A152773 * A033567 A181156 A162394
Adjacent sequences: A039592 A039593 A039594 * A039596 A039597 A039598
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KEYWORD
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nonn,fini,full
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AUTHOR
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Felice Russo
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STATUS
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approved
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