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 A131259 a(2n)=A000217(n), a(2n+1)=-2*A000217(n). 1
 0, 0, 1, -2, 3, -6, 6, -12, 10, -20, 15, -30, 21, -42, 28, -56, 36, -72, 45, -90, 55, -110, 66, -132, 78, -156, 91, -182, 105, -210, 120, -240, 136, -272, 153, -306, 171, -342, 190, -380, 210, -420, 231, -462, 253, -506, 276, -552, 300, -600, 325, -650, 351, -702, 378, -756, 406, -812, 435, -870, 465, -930, 496, -992 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Table of n, a(n) for n=0..63. Index entries for linear recurrences with constant coefficients, signature (0,3,0,-3,0,1). FORMULA O.g.f.: ogf217(x^2) - 2*x*ogf217(x^2) = x^2/(1-x^2)^3 - 2*x^3/(1-x^2) = x^2*(1 - 2*x) / (1 - x^2)^3. - Georg Fischer, Nov 16 2022 MAPLE A000217 := proc(n) n*(n+1)/2 ; end: A131259 := proc(n) if n mod 2 = 0 then A000217(n/2) ; else -2*A000217((n-1)/2) ; fi ; end: seq(A131259(n), n=0..60) ; # R. J. Mathar, Oct 26 2007 MATHEMATICA CoefficientList[Series[x^2*(1 - 2*x)/(1 - x^2)^3, {x, 0, 35}], x] (* Georg Fischer, Nov 16 2022 *) CROSSREFS Cf. A000217, A129819. Sequence in context: A363075 A119319 A069808 * A346758 A143177 A129648 Adjacent sequences: A131256 A131257 A131258 * A131260 A131261 A131262 KEYWORD sign,easy AUTHOR Paul Curtz, Sep 28 2007 EXTENSIONS More terms from R. J. Mathar, Oct 26 2007 STATUS approved

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Last modified February 25 06:40 EST 2024. Contains 370310 sequences. (Running on oeis4.)