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 A203243 Second elementary symmetric function of the first n terms of (1,3,9,27,81,...). 4
 3, 39, 390, 3630, 33033, 298389, 2688780, 24208860, 217909263, 1961271939, 17651713170, 158866215690, 1429798332693, 12868192168689, 115813751041560, 1042323823944120, 9380914609207323, 84428232063996639, 759854090319361950 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 LINKS Index entries for linear recurrences with constant coefficients, signature (13,-39,27). FORMULA a(n) =3*A006100(n). From Colin Barker, Aug 15 2014: (Start) a(n) = (3-4*3^n+9^n)/16. a(n) = 13*a(n-1)-39*a(n-2)+27*a(n-3). G.f.: -3*x^2 / ((x-1)*(3*x-1)*(9*x-1)). (End) MATHEMATICA f[k_] := 3^(k - 1); t[n_] := Table[f[k], {k, 1, n}] a[n_] := SymmetricPolynomial[2, t[n]] Table[a[n], {n, 2, 32}]    (* A203243 *) Table[a[n]/3, {n, 2, 32}]  (* A006100 *) PROG (PARI) Vec(-3*x^2/((x-1)*(3*x-1)*(9*x-1)) + O(x^100)) \\ Colin Barker, Aug 15 2014 CROSSREFS Cf. A006100. Sequence in context: A050392 A292294 A191468 * A063035 A198970 A014850 Adjacent sequences:  A203240 A203241 A203242 * A203244 A203245 A203246 KEYWORD nonn,easy AUTHOR Clark Kimberling, Dec 31 2011 STATUS approved

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Last modified July 26 12:20 EDT 2021. Contains 346294 sequences. (Running on oeis4.)