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Search: id:A140973
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| A140973 |
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Numbers n such that arithmetic mean of squares of the first n Tribonacci numbers is an integer. |
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+0
2
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| 1, 2, 8, 15, 16, 18, 22, 32, 47, 48, 53, 58, 64, 70, 77, 78, 80, 94, 95, 96, 103, 106, 128, 138, 163, 199, 206, 256, 257, 266, 269, 311, 326, 330, 352, 358, 385, 397, 398, 401, 419, 421, 499, 512, 514, 538, 587, 599, 617, 622, 640, 672, 683, 757, 768, 770, 773
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OFFSET
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1,2
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COMMENT
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Could arithmetic tribonacci mean (T(0)+...+T(n-1)) / n be an integer ?
The arithmetic means are integers for the first 1, 2, 47, 53, 94, 103, 106 etc. tribonacci numbers. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 04 2008]
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FORMULA
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n such that (T(0)^2+ T(1)^2+ ... + T(n-1)^2) / n is an integer. T(i) i-th Tribonacci number.
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CROSSREFS
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Cf. A000073.
Cf. A107239. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 04 2008]
Sequence in context: A055258 A054981 A059449 this_sequence A065907 A031272 A063286
Adjacent sequences: A140970 A140971 A140972 this_sequence A140974 A140975 A140976
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KEYWORD
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easy,nonn
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AUTHOR
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Ctibor O. Zizka (ctibor.zizka(AT)seznam.cz), Jul 27 2008
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EXTENSIONS
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Added 1 and 2 and extended from 32 on, R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 04 2008
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