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 A116138 (n^2+n)*3^n. 2
 0, 6, 54, 324, 1620, 7290, 30618, 122472, 472392, 1771470, 6495390, 23383404, 82904796, 290166786, 1004423490, 3443737680, 11708708112, 39516889878, 132497807238, 441659357460, 1464449448420, 4832683179786, 15878816162154 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Index to sequences with linear recurrences with constant coefficients, signature (9,-27,27). FORMULA G.f.: 6*x/(1-3*x)^3. a(n)=6*A027472(n+2). - R. J. Mathar, Dec 19 2008 a(n) = 9*a(n-1)-27*a(n-2)+27*a(n-3). - Vincenzo Librandi, Feb 28 2013 MATHEMATICA Table[(n^2 + n) 3^n, {n, 0, 30}] (* Vincenzo Librandi, Feb 28 2013 *) PROG (MAGMA) [(n^2+n)*3^n: n in [0..25]]; /* or */ I:=[0, 6, 54]; [n le 3 select I[n] else 9*Self(n-1)-27*Self(n-2)+27*Self(n-3): n in [1..30]]; // Vincenzo Librandi, Feb 28 2013 (PARI) a(n)=(n^2+n)*3^n \\ Charles R Greathouse IV, Feb 28 2013 CROSSREFS Cf. A007758, A036289, A128796, A027472. Sequence in context: A153333 A195901 A072368 * A060774 A043026 A125837 Adjacent sequences:  A116135 A116136 A116137 * A116139 A116140 A116141 KEYWORD nonn,easy AUTHOR Mohammad K. Azarian, Apr 08 2007 STATUS approved

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