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1, 3, 12, 27, 108, 243, 972, 2187, 8748, 19683, 78732, 177147, 708588, 1594323, 6377292, 14348907, 57395628, 129140163, 516560652, 1162261467, 4649045868, 10460353203, 41841412812, 94143178827, 376572715308
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history;
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OFFSET
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0,2
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COMMENTS
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A133646 is a companion case.
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LINKS
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Harvey P. Dale, Table of n, a(n) for n = 0..1000
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FORMULA
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A133566 * A000244, where A133566 = an infinite lower triangular matrix and A000244 = [3^0, 3^1, 3^2, ...]. For odd n, a(n) = 3^n. For even n, a(n) = 4 * 3^(n-1).
G.f.: (1+3*x+3*x^2)/(1-9*x^2). - Philippe Deléham, Apr 06 2012
a(n+2) = 9*a(n), a(0) = 1, a(1) = 3, a(2) = 12. - Philippe Deléham, Apr 06 2012
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EXAMPLE
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a(3) = 27 = 3^3.
a(4) = 108 = 4 * 3^3.
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MATHEMATICA
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Join[{1}, Flatten[NestList[9#&, {3, 12}, 20]]] (* or *) LinearRecurrence[{0, 9}, {1, 3, 12}, 40] (* Harvey P. Dale, Aug 01 2019 *)
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CROSSREFS
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Cf. A133566, A133646, A000244.
Sequence in context: A009259 A183503 A216713 * A009222 A260815 A083543
Adjacent sequences: A133644 A133645 A133646 * A133648 A133649 A133650
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KEYWORD
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nonn
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AUTHOR
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Gary W. Adamson, Sep 19 2007
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EXTENSIONS
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More terms from Philippe Deléham, Apr 06 2012
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STATUS
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approved
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