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URL: https://oeis.org/A077993

⇱ A077993 - OEIS

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A077993
Expansion of 1/(1+2*x+2*x^2+2*x^3).
3
1, -2, 2, -2, 4, -8, 12, -16, 24, -40, 64, -96, 144, -224, 352, -544, 832, -1280, 1984, -3072, 4736, -7296, 11264, -17408, 26880, -41472, 64000, -98816, 152576, -235520, 363520, -561152, 866304, -1337344, 2064384, -3186688, 4919296, -7593984, 11722752, -18096128, 27934720, -43122688
OFFSET
0,2
FORMULA
a(n) = (-1)^n * A077943(n). - R. J. Mathar, Aug 04 2008
MATHEMATICA
LinearRecurrence[{-2, -2, -2}, {1, -2, 2}, 50] (* or *) CoefficientList[ Series[1/(1+2*x+2*x^2+2*x^3), {x, 0, 50}], x] (* G. C. Greubel, Jun 27 2019 *)
PROG
(PARI) my(x='x+O('x^50)); Vec(1/(1+2*x+2*x^2+2*x^3)) \\ G. C. Greubel, Jun 27 2019
(Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( 1/(1+2*x+2*x^2+2*x^3) )); // G. C. Greubel, Jun 27 2019
(SageMath) (1/(1+2*x+2*x^2+2*x^3)).series(x, 50).coefficients(x, sparse=False) # G. C. Greubel, Jun 27 2019
(GAP) a:=[1, -2, 2];; for n in [4..50] do a[n]:=-2*(a[n-1]+a[n-2]+a[n-3]); od; a; # G. C. Greubel, Jun 27 2019
CROSSREFS
Cf. A077943.
Sequence in context: A326022 A346047 A077943 * A302613 A295680 A099768
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Nov 17 2002
STATUS
approved