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 A083392 Alternating partial sums of A000217. 7
 0, -1, 2, -4, 6, -9, 12, -16, 20, -25, 30, -36, 42, -49, 56, -64, 72, -81, 90, -100, 110, -121, 132, -144, 156, -169, 182, -196, 210, -225, 240, -256, 272, -289, 306, -324, 342, -361, 380, -400, 420, -441, 462, -484, 506, -529, 552, -576, 600, -625, 650, -676, 702 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS William A. Tedeschi, Table of n, a(n) for n = 0..10000 Index entries for linear recurrences with constant coefficients, signature (-2, 0, 2, 1). FORMULA a(n) = Sum_{i=0..n} (-1)^i*t(i) where t(i) = i*(i+1)/2. From R. J. Mathar, Feb 09 2010: (Start) a(n) = -2*a(n-1) + 2*a(n-3) + a(n-4). G.f.: x/((x-1)*(1+x)^3). (End) a(n) = (-1)^n * ((n^2+n)/2 - floor(n^2/4)). - William A. Tedeschi, Aug 24 2010 EXAMPLE a(4) = t(0) - t(1) + t(2) - t(3) + t(4) = 0 - 1 + 3 - 6 + 10 = 6. MATHEMATICA LinearRecurrence[{-2, 0, 2, 1}, {0, -1, 2, -4}, 60] (* Harvey P. Dale, Mar 16 2016 *) PROG (PARI) t(n)=n*(n+1)/2; for (n=0, 30, print1(sum(i=0, n, (-1)^i*t(i)), ", ")) (MAGMA) [(-1)^n*((n^2+n)/2 - Floor(n^2/4)): n in [0..50]]; // G. C. Greubel, Oct 29 2017 CROSSREFS Cf. A000217, A002620. Sequence in context: A194254 A086378 A088900 * A076921 A002620 A087811 Adjacent sequences:  A083389 A083390 A083391 * A083393 A083394 A083395 KEYWORD sign,easy AUTHOR Jon Perry, Jun 11 2003 EXTENSIONS More terms from David W. Wilson, Jun 14 2003 STATUS approved

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Last modified January 16 03:55 EST 2019. Contains 319184 sequences. (Running on oeis4.)