A131386 a(n) = (-1)^n*n*(n-2).

1, 0, -3, 8, -15, 24, -35, 48, -63, 80, -99, 120, -143, 168, -195, 224, -255, 288, -323, 360, -399, 440, -483, 528, -575, 624, -675, 728, -783, 840, -899, 960, -1023, 1088, -1155, 1224, -1295, 1368, -1443, 1520, -1599, 1680, -1763, 1848, -1935, 2024, -2115, 2208, -2303, 2400

Offset

1,3

Links

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

P. Barry, A. Hennessy, Meixner-Type Results for Riordan Arrays and Associated Integer Sequences, J. Int. Seq. 13 (2010) # 10.9.4, section 9.

Index entries for linear recurrences with constant coefficients, signature (-3,-3,-1).

Formula

From R. J. Mathar, Dec 07 2009: (Start)

a(n) = -3*a(n-1) - 3*a(n-2) - a(n-3).

G.f.: x*(1+3*x)/(1+x)^3. (End)

Sum_{n>2} 1/a(n) = -1/4. - Enrique Pérez Herrero, Dec 19 2015

Mathematica

Table[(-1)^n*n*(n - 2), {n, 80}] (* Vladimir Joseph Stephan Orlovsky, Feb 14 2012 *)
CoefficientList[Series[(1+3*x)/(1+x)^3, {x, 0, 50}], x] (* Vincenzo Librandi, Jul 09 2012 *)
LinearRecurrence[{-3, -3, -1}, {1, 0, -3}, 50] (* Harvey P. Dale, Aug 25 2023 *)

Prog

(Magma) [(-1)^n*n*(n-2): n in [1..50]]; // Vincenzo Librandi, Jul 09 2012
(PARI) Vec(x*(1+3*x)/(1+x)^3 + O(x^100)) \\ Altug Alkan, Dec 19 2015

Crossrefs

Cf. A067998.

Sequence in context: A083656 A013648 A258837 * A132411 A005563 A067998

Adjacent sequences: A131383 A131384 A131385 * A131387 A131388 A131389

Keyword

sign,easy

Author

Jamel Ghanouchi, Aug 26 2008

Extensions

Entry completely rewriten by Jamel Ghanouchi, Nov 02 2009

Terms corrected by Jamel Ghanouchi, Nov 07 2009

Definition clarified; zeros skipped; sequence extended - R. J. Mathar, Dec 07 2009

Status

approved