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A147296
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a(n) = n*(9*n+2).
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4
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0, 11, 40, 87, 152, 235, 336, 455, 592, 747, 920, 1111, 1320, 1547, 1792, 2055, 2336, 2635, 2952, 3287, 3640, 4011, 4400, 4807, 5232, 5675, 6136, 6615, 7112, 7627, 8160, 8711, 9280, 9867, 10472, 11095, 11736, 12395, 13072, 13767, 14480, 15211, 15960
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OFFSET
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0,2
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COMMENTS
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For n >= 1, the continued fraction expansion of sqrt(4*a(n)) is [6n; {1, 1, 1, 3n-1, 1, 1, 1, 12n}]. - Magus K. Chu, Sep 17 2022
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LINKS
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FORMULA
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a(n) = n*(9*n + 2), as conjectured by V. Librandi. - From M. F. Hasler, Mar 01 2009
G.f.: x*(11+7*x)/(1-x)^3. - Jaume Oliver Lafont, Aug 30 2009
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MATHEMATICA
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Table[n(9n+2), {n, 0, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {0, 11, 40}, 50] (* Harvey P. Dale, Dec 19 2014 *)
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PROG
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CROSSREFS
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Equals first 9-fold decimation of A144454.
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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