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A097321
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(3*n-1) * 3*n * (3*n+1).
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4
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24, 210, 720, 1716, 3360, 5814, 9240, 13800, 19656, 26970, 35904, 46620, 59280, 74046, 91080, 110544, 132600, 157410, 185136, 215940, 249984, 287430, 328440, 373176, 421800, 474474, 531360, 592620, 658416, 728910, 804264, 884640
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| log(3) = lim [n->infinity, 1/a(n)].
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..10000
S. Ramanujan, Notebook entry
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FORMULA
| G.f.: 6x * (4x^2 + 19x + 4) / (1-x)^4.
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MATHEMATICA
| Table[27n^3-3n, {n, 40}] (* From Harvey P. Dale, Mar 30 2011 *)
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PROG
| (MAGMA) [27*n^3-3*n: n in [1..40]]; // Vincenzo Librandi, Sep 07 2011
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CROSSREFS
| Cf. A069072, A069140, A002391, A016767.
Sequence in context: A055857 A047659 A108671 * A105946 A050222 A169635
Adjacent sequences: A097318 A097319 A097320 * A097322 A097323 A097324
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KEYWORD
| nonn,easy
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AUTHOR
| Ralf Stephan, Aug 07 2004
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