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A083423
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a(n) = (5*3^n + (-3)^n)/6.
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1
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1, 2, 9, 18, 81, 162, 729, 1458, 6561, 13122, 59049, 118098, 531441, 1062882, 4782969, 9565938, 43046721, 86093442, 387420489, 774840978, 3486784401, 6973568802, 31381059609, 62762119218, 282429536481, 564859072962
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OFFSET
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0,2
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LINKS
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Table of n, a(n) for n=0..25.
Index entries for linear recurrences with constant coefficients, signature (0,9)
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FORMULA
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From Reinhard Zumkeller, Mar 04 2011: (Start)
G.f.: (1+2x)/((1-3x)*(1+3x)).
E.g.f.: (5*exp(3x) + exp(-3x))/6.
a(n+3) = a(n+2)*a(n+1)/a(n). (End)
a(n) = 9*a(n-2). - Vincenzo Librandi, Mar 20 2011
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MATHEMATICA
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LinearRecurrence[{0, 9}, {1, 2}, 30] (* Harvey P. Dale, Dec 04 2019 *)
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CROSSREFS
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Cf. A083424.
Sequence in context: A280588 A191520 A037421 * A068978 A006226 A109298
Adjacent sequences: A083420 A083421 A083422 * A083424 A083425 A083426
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry, Apr 30 2003
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STATUS
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approved
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