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 A028494 a(n) = -(1/2)*(n+2)*(n^2 - 6*n - 1). 1
 1, 9, 18, 25, 27, 21, 4, -27, -75, -143, -234, -351, -497, -675, -888, -1139, -1431, -1767, -2150, -2583, -3069, -3611, -4212, -4875, -5603, -6399, -7266, -8207, -9225, -10323, -11504, -12771, -14127, -15575, -17118, -18759, -20501, -22347 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..740 Index entries for linear recurrences with constant coefficients, signature (4, -6, 4, -1). MATHEMATICA Table[-(1/2)(n+2)(n^2-6n-1), {n, 0, 40}] (* or *) LinearRecurrence[{4, -6, 4, -1}, {1, 9, 18, 25}, 40] (* Harvey P. Dale, Sep 08 2018 *) PROG (Magma) [-1/2*(n+2)*(n^2-6*n-1): n in [0..40]]; // Vincenzo Librandi, Apr 27 2011 (PARI) a(n)=-(n+2)*(n^2-6*n-1)/2 \\ Charles R Greathouse IV, Oct 18 2022 CROSSREFS Sequence in context: A232056 A109661 A015798 * A167663 A347242 A038838 Adjacent sequences: A028491 A028492 A028493 * A028495 A028496 A028497 KEYWORD sign,easy AUTHOR N. J. A. Sloane STATUS approved

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Last modified September 27 17:14 EDT 2023. Contains 365714 sequences. (Running on oeis4.)