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Search: id:A092236
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| A092236 |
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(3^n + 2*3^(n/2)*cos(n*Pi/6))/3. |
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+0
1
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| 1, 2, 4, 9, 24, 72, 225, 702, 2160, 6561, 19764, 59292, 177633, 532170, 1595052, 4782969, 14346720, 43040160, 129127041, 387400806, 1162241784, 3486784401, 10460412252, 31381236756, 94143533121, 282430067922, 847289140884, 2541865828329, 7625595890664
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OFFSET
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0,2
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COMMENT
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From an Internat. Math. Olympiad problem.
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REFERENCES
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E. Lozansky and C. Rousseau, Winning Solutions, Springer, 1996; see p. 154.
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FORMULA
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G.f.: (1-4x+4x^2) / [(1-3x)(1-3x+3x^2)].
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CROSSREFS
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Sequence in context: A148084 A156804 A081913 this_sequence A009283 A125654 A141824
Adjacent sequences: A092233 A092234 A092235 this_sequence A092237 A092238 A092239
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Feb 18 2004
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