A128801 a(n) = n*(n-1)*7^n.

0, 98, 2058, 28812, 336140, 3529470, 34588806, 322828856, 2905459704, 25422772410, 217505941730, 1827049910532, 15114685623492, 123436599258518, 996987917088030, 7975903336704240, 63275499804520304, 498294560960597394

Offset

1,2

Links

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

Index entries for linear recurrences with constant coefficients, signature (21,-147,343).

Formula

G.f.: 98*x^2/(1-7*x)^3. - Emeric Deutsch, May 04 2007

a(n) = 21*a(n-1) - 147*a(n-2) + 343*a(n-3). - Vincenzo Librandi, Feb 12 2013

a(n) = 98*A027474(n). - R. J. Mathar, Apr 26 2015

Maple

g:=98*x^2/(1-7*x)^3: gser:=series(g, x=0, 22): seq(coeff(gser, x, n), n=1..18); # Emeric Deutsch, May 04 2007

Mathematica

LinearRecurrence[{21, -147, 343}, {0, 98, 2058}, 30] (* Vincenzo Librandi, Feb 12 2013 *)

Prog

(Magma) [(n^2-n)*7^n: n in [1..25]] // Vincenzo Librandi, Feb 12 2013

Crossrefs

Cf. A036289, A007758.

Sequence in context: A285045 A197616 A022149 * A188484 A271037 A243477

Adjacent sequences: A128798 A128799 A128800 * A128802 A128803 A128804

Keyword

nonn,easy

Author

Mohammad K. Azarian, Apr 07 2007

Status

approved