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URL: https://oeis.org/A077952

⇱ A077952 - OEIS

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A077952
Expansion of 1/(1 - x + x^2 + 2*x^3).
3
1, 1, 0, -3, -5, -2, 9, 21, 16, -23, -81, -90, 37, 289, 432, 69, -941, -1874, -1071, 2685, 7504, 6961, -5913, -27882, -35891, 3817, 95472, 163437, 60331, -294050, -681255, -507867, 761488, 2631865, 2886111, -1268730, -9418571, -13922063, -1966032, 30793173, 60603331, 33742222, -88447455
OFFSET
0,4
COMMENTS
Row sums of Riordan array (1, x*(1-x-2*x^2)). - Paul Barry, Mar 09 2006
FORMULA
a(n) = Sum_{k=0..n} Sum_{j=0..n} C(k,j-k)*C(k,n-j)*(-2)^(n-j). - Paul Barry, Mar 09 2006
a(n) = (-1)^n*A077975(n). - R. J. Mathar, Jul 31 2010
MAPLE
seq(coeff(series(1/(1-x+x^2+2*x^3), x, n+1), x, n), n = 0 .. 50); # G. C. Greubel, Aug 07 2019
MATHEMATICA
LinearRecurrence[{1, -1, -2}, {1, 1, 0}, 50] (* or *) CoefficientList[Series[ 1/(1-x+x^2+2*x^3), {x, 0, 50}], x] (* G. C. Greubel, Aug 07 2019 *)
PROG
(PARI) Vec(1/(1-x+x^2+2*x^3)+O(x^50)) \\ Charles R Greathouse IV, Sep 27 2012
(Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( 1/(1-x+x^2+2*x^3) )); // G. C. Greubel, Aug 07 2019
(SageMath) (1/(1-x+x^2+2*x^3)).series(x, 50).coefficients(x, sparse=False) # G. C. Greubel, Aug 07 2019
(GAP) a:=[1, 1, 0];; for n in [4..50] do a[n]:=a[n-1]-a[n-2]-2*a[n-3]; od; a; # G. C. Greubel, Aug 07 2019
CROSSREFS
Sequence in context: A003574 A101157 A193725 * A077975 A356378 A258656
KEYWORD
sign,easy
AUTHOR
N. J. A. Sloane, Nov 17 2002
STATUS
approved