A128786 - OEIS

A128786

n^2*7^n.

0, 7, 196, 3087, 38416, 420175, 4235364, 40353607, 368947264, 3268642167, 28247524900, 239256535903, 1993145356944, 16374242758783, 132931722278404, 1068201339737175, 8507630225817856, 67230218542302823, 527606005722985476

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OFFSET

0,2

LINKS

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

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

FORMULA

G.f.: 7*x*(1 + 7*x)/((1 - 7*x)^3). - Vincenzo Librandi, Feb 06 2013

a(n) = 21*a(n-1) - 147*a(n-2) + 343*a(n-3). - Vincenzo Librandi, Feb 06 2013

MATHEMATICA

LinearRecurrence[{21, -147, 343}, {0, 7, 196}, 40] (* Vincenzo Librandi, Feb 06 2013 *)

PROG

(Magma) [n^2*7^n: n in [0..20]]; // Vincenzo Librandi, Feb 06 2013

CROSSREFS

Cf. A036289; A007758.

Sequence in context: A135809 A182268 A156359 * A034835 A041371 A136675

Adjacent sequences: A128783 A128784 A128785 * A128787 A128788 A128789

KEYWORD

nonn,easy

AUTHOR

Mohammad K. Azarian, Apr 07 2007

STATUS

approved