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 A131386 a(n) = (-1)^n*n*(n-2). 3
 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 (list; graph; refs; listen; history; text; internal format)
 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 *) 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

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Last modified April 17 08:40 EDT 2021. Contains 343064 sequences. (Running on oeis4.)