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 A133647 A133566 * A000244. 2
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A133646 is a companion case. LINKS Harvey P. Dale, Table of n, a(n) for n = 0..1000 FORMULA 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 EXAMPLE a(3) = 27 = 3^3. a(4) = 108 = 4 * 3^3. MATHEMATICA Join[{1}, Flatten[NestList[9#&, {3, 12}, 20]]] (* or *) LinearRecurrence[{0, 9}, {1, 3, 12}, 40] (* Harvey P. Dale, Aug 01 2019 *) CROSSREFS Cf. A133566, A133646, A000244. Sequence in context: A009259 A183503 A216713 * A009222 A260815 A083543 Adjacent sequences:  A133644 A133645 A133646 * A133648 A133649 A133650 KEYWORD nonn AUTHOR Gary W. Adamson, Sep 19 2007 EXTENSIONS More terms from Philippe Deléham, Apr 06 2012 STATUS approved

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Last modified February 25 20:04 EST 2020. Contains 332258 sequences. (Running on oeis4.)