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 A008733 Molien series for 3-dimensional group [2+, n] = 2*(n/2). 2
 1, 0, 2, 1, 4, 2, 6, 4, 9, 6, 12, 9, 16, 12, 20, 16, 25, 20, 30, 25, 36, 30, 42, 36, 49, 42, 56, 49, 64, 56, 72, 64, 81, 72, 90, 81, 100, 90, 110, 100, 121, 110, 132, 121, 144, 132, 156, 144, 169, 156, 182, 169, 196, 182, 210, 196, 225, 210, 240, 225, 256 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (1,1,-1,1,-1,-1,1). FORMULA From R. J. Mathar, Nov 04 2008: (Start) a(n) = A005232(n) - A005232(n-1). G.f.: (1-x+x^2)/((1-x)^3*(1+x)^2*(1+x^2)). (End) a(n) = floor((n^2 + 5*n + 13 + 3*(n+1)*(-1)^n)/16). - Tani Akinari, Aug 23 2013 a(n) = Sum_{i=1..floor((n+4)/2)} floor((i-(n mod 2))/2). - Wesley Ivan Hurt, Mar 31 2014 a(n) = (2*n^2+10*n+13+3*(2*n+5)*(-1)^n+4*(-1)^((6*n-1+(-1)^n)/4))/32. - Luce ETIENNE, Jun 09 2015 MATHEMATICA CoefficientList[Series[(1+x^3)/((1-x^2)^2*(1-x^4)), {x, 0, 70}], x] (* Vincenzo Librandi, Aug 24 2013 *) LinearRecurrence[{1, 1, -1, 1, -1, -1, 1}, {1, 0, 2, 1, 4, 2, 6}, 70] (* Harvey P. Dale, Nov 23 2015 *) PROG (MAGMA) [Floor((n^2+5*n+13+3*(n+1)*(-1)^n)/16): n in [0..70]]; // Vincenzo Librandi, Aug 24 2013 (PARI) a(n)=((n^2+5*n+13+3*(n+1)*(-1)^n))\16 \\ Charles R Greathouse IV, Jun 11 2015 (Sage) [floor((n^2 + 5*n + 13 + 3*(n+1)*(-1)^n)/16) for n in (0..70)] # G. C. Greubel, Jul 30 2019 (GAP) List([0..70], n-> Int((n^2 + 5*n + 13 + 3*(n+1)*(-1)^n)/16)); # G. C. Greubel, Jul 30 2019 CROSSREFS Sequence in context: A194747 A065423 A239242 * A244515 A154280 A004795 Adjacent sequences:  A008730 A008731 A008732 * A008734 A008735 A008736 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified October 19 16:17 EDT 2019. Contains 328223 sequences. (Running on oeis4.)