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A128969 a(n) = (n^3 - n)*9^n. 1
0, 486, 17496, 393660, 7085880, 111602610, 1607077584, 21695547384, 278942752080, 3451916556990, 41422998683880, 484649084601396, 5551434969070536, 62453643402043530, 691794203838020640 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (36,-486,2916,-6561).

FORMULA

G.f.: 486x^2/(1-9x)^4. a(n)=486*A038291(n+1,3). - R. J. Mathar, Dec 19 2008

a(n) = 36*a(n-1) -486*a(n-2) +2916*a(n-3) -6561*a(n-4). - Vincenzo Librandi, Feb 11 2013

MATHEMATICA

CoefficientList[Series[486 x/(1 - 9 x)^4, {x, 0, 30}], x] (* Vincenzo Librandi, Feb 11 2013 *)

PROG

(MAGMA) [(n^3-n)*9^n: n in [0..25]]; (* or *) I:=[0, 486, 17496, 393660]; [n le 4 select I[n] else 36*Self(n-1) - 486*Self(n-2) + 2916*Self(n-3) - 6561*Self(n-4): n in [1..25]]; // Vincenzo Librandi, Feb 11 2013

CROSSREFS

Cf. A128796, A036289.

Sequence in context: A187860 A205240 A206146 * A223412 A097765 A179428

Adjacent sequences:  A128966 A128967 A128968 * A128970 A128971 A128972

KEYWORD

nonn,easy

AUTHOR

Mohammad K. Azarian, Apr 28 2007

EXTENSIONS

Offset corrected by Mohammad K. Azarian, Nov 20 2008

STATUS

approved

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Last modified December 14 22:42 EST 2019. Contains 329987 sequences. (Running on oeis4.)