A129009 a(n) = (n^3 + n^2)*9^n.
18, 972, 26244, 524880, 8857350, 133923132, 1874923848, 24794911296, 313810596090, 3835462841100, 45565298552268, 528708092292432, 6014054549826414, 67257769817585340, 741208075540736400
Offset: 1
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).
Programs
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Magma
[(n^3+n^2)*9^n: n in [1..25]]; // Vincenzo Librandi, Feb 12 2013
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Magma
I:=[18,972,26244,524880]; [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 12 2013
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Mathematica
LinearRecurrence[{36, -486, 2916, -6561}, {18, 972, 26244, 524880}, 30] (* Vincenzo Librandi, Feb 12 2013 *)
Formula
G.f.: 18*x*(1+18*x)/(1-9*x)^4. - 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 12 2013