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A053730 2^(n-2)*(n^2-n+4). 2
1, 2, 6, 20, 64, 192, 544, 1472, 3840, 9728, 24064, 58368, 139264, 327680, 761856, 1753088, 3997696, 9043968, 20316160, 45350912, 100663296, 222298112, 488636416, 1069547520, 2332033024, 5066719232, 10972299264, 23689428992 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (6,-12,8).

FORMULA

G.f.: (1-4*x+6*x^2)/(1-2*x)^3. [Colin Barker, Apr 01 2012]

a(n) = 6*a(n-1) - 12*a(n-2) + 8*a(n-3). _ Vincenzo Librandi_, Apr 28 2012

a(n) = Sum_{k=0..n} binomial(n,k) * A077028(n,k), where A077028(n,k) = (n-k)*k + 1. - Paul D. Hanna, Oct 11 2015

MATHEMATICA

CoefficientList[Series[(1-4*x+6*x^2)/(1-2*x)^3, {x, 0, 30}], x] (* Vincenzo Librandi, Apr 28 2012 *)

PROG

(MAGMA) I:=[1, 2, 6]; [n le 3 select I[n] else 6*Self(n-1)-12*Self(n-2)+8*Self(n-3): n in [1..30]]; // Vincenzo Librandi, Apr 28 2012

CROSSREFS

Cf. A053545.

Sequence in context: A177792 A193235 A199102 * A220874 A273902 A181301

Adjacent sequences:  A053727 A053728 A053729 * A053731 A053732 A053733

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Mar 24 2000

STATUS

approved

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Last modified December 6 08:53 EST 2016. Contains 278775 sequences.