A128991 a(n) = (n^3 - n^2)*8^n.

0, 256, 9216, 196608, 3276800, 47185920, 616562688, 7516192768, 86973087744, 966367641600, 10393820856320, 108851651149824, 1114904790564864, 11206222510292992, 110830772079820800, 1080863910568919040

Offset

1,2

Links

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

Index entries for linear recurrences with constant coefficients, signature (32,-384,2048,-4096).

Formula

G.f.: 256*x^2*(1+4*x)/(1-8*x)^4. - Vincenzo Librandi, Feb 12 2013

a(n) = 32*a(n-1)-384*a(n-2)+2048*a(n-3)-4096*a(n-4). - Vincenzo Librandi, Feb 12 2013

Mathematica

CoefficientList[Series[256 x (1 + 4 x)/(1 - 8 x)^4, {x, 0, 30}], x] (* Vincenzo Librandi, Feb 12 2013 *)
LinearRecurrence[{32, -384, 2048, -4096}, {0, 256, 9216, 196608}, 30] (* Harvey P. Dale, Aug 25 2013 *)

Prog

(Magma) [(n^3-n^2)*8^n: n in [1..25]]; /* or */ I:=[0, 256, 9216, 196608]; [n le 4 select I[n] else 32*Self(n-1)-384*Self(n-2)+2048*Self(n-3)-4096*Self(n-4): n in [1..25]]; // Vincenzo Librandi, Feb 12 2013

Crossrefs

Cf. A128796, A036289.

Sequence in context: A232959 A187955 A253135 * A230973 A191680 A191496

Adjacent sequences: A128988 A128989 A128990 * A128992 A128993 A128994

Keyword

nonn,easy

Author

Mohammad K. Azarian, Apr 30 2007

Extensions

Offset corrected by Mohammad K. Azarian, Nov 20 2008

Status

approved