A077971 - OEIS

A077971

Expansion of 1/(1+x-x^2-2*x^3).

1, -1, 2, -1, 1, 2, -3, 7, -6, 7, 1, -6, 21, -25, 34, -17, 1, 50, -83, 135, -118, 87, 65, -214, 453, -537, 562, -193, -319, 1250, -1955, 2567, -2022, 679, 2433, -5798, 9589, -10521, 8514, 143, -12671, 29842, -42227, 46727, -29270, -8457, 72641, -139638, 195365, -189721, 105810, 95199, -368831

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OFFSET

0,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (-1,1,2).

FORMULA

a(n) = (-1)^n * A077948(n). - G. C. Greubel, Jun 24 2019

MATHEMATICA

LinearRecurrence[{-1, 1, 2}, {1, -1, 2}, 60] (* or *) CoefficientList[Series[ 1/(1 +x-x^2-2*x^3), {x, 0, 60}], x] (* G. C. Greubel, Jun 24 2019 *)

PROG

(PARI) Vec(1/(1+x-x^2-2*x^3)+O(x^60)) \\ Charles R Greathouse IV, Sep 26 2012

(Magma) R<x>:=PowerSeriesRing(Integers(), 60); Coefficients(R!( 1/(1+x-x^2-2*x^3) )); // G. C. Greubel, Jun 24 2019

(Sage) (1/(1+x-x^2-2*x^3)).series(x, 60).coefficients(x, sparse=False) # G. C. Greubel, Jun 24 2019

(GAP) a:=[1, -1, 2];; for n in [4..60] do a[n]:=-a[n-1]+a[n-2]+2*a[n-3]; od; a; # G. C. Greubel, Jun 24 2019

CROSSREFS

Cf. A077948.

First differences of A077901.

Sequence in context: A284999 A016732 A077948 * A030018 A010739 A166918

Adjacent sequences: A077968 A077969 A077970 * A077972 A077973 A077974

KEYWORD

sign,easy

AUTHOR

N. J. A. Sloane, Nov 17 2002

STATUS

approved