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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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FORMULA
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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)
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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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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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