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 A131174 a(2n) = 2*A000217(n), a(2n+1) = A000217(n). 1
 0, 0, 2, 1, 6, 3, 12, 6, 20, 10, 30, 15, 42, 21, 56, 28, 72, 36, 90, 45, 110, 55, 132, 66, 156, 78, 182, 91, 210, 105, 240, 120, 272, 136, 306, 153, 342, 171, 380, 190, 420, 210, 462, 231, 506, 253, 552, 276, 600, 300, 650, 325, 702, 351, 756, 378, 812, 406, 870, 435 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Harvey P. Dale, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (0, 3, 0, -3, 0, 1). FORMULA a(n) = 3*a(n-2)-3*a(n-4)+a(n-6). G.f.: x^2*(2+x)/((1-x)^3*(1+x)^3). [R. J. Mathar, Jul 17 2009] a(n) = (3*n^2+4*n-1+(n^2+4*n+1)*(-1)^n)/16. - Luce ETIENNE, Aug 19 2014 MAPLE A000217 := proc(n) n*(n+1)/2 ; end: A131174 := proc(n) if n mod 2 = 0 then 2*A000217(n/2) ; else A000217((n-1)/2) ; fi ; end: seq(A131174(n), n=0..90) ; # R. J. Mathar, Oct 26 2007 MATHEMATICA LinearRecurrence[{0, 3, 0, -3, 0, 1}, {0, 0, 2, 1, 6, 3}, 60] (* Harvey P. Dale, Jun 01 2012 *) CROSSREFS Sequence in context: A050137 A086111 A262603 * A291539 A135994 A217646 Adjacent sequences:  A131171 A131172 A131173 * A131175 A131176 A131177 KEYWORD nonn AUTHOR Paul Curtz, Sep 24 2007 EXTENSIONS Edited by N. J. A. Sloane, Sep 27 2007 More terms from R. J. Mathar, Oct 26 2007 STATUS approved

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Last modified August 11 06:25 EDT 2020. Contains 336422 sequences. (Running on oeis4.)