# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a077981 Showing 1-1 of 1 %I A077981 #14 Sep 08 2022 08:45:08 %S A077981 1,-2,6,-14,36,-88,220,-544,1352,-3352,8320,-20640,51216,-127072, %T A077981 315296,-782304,1941056,-4816128,11949760,-29649664,73566592, %U A077981 -182532992,452899840,-1123732480,2788198656,-6918062592,17165057536,-42589842944,105673675776,-262196922368 %N A077981 Expansion of 1/(1+2*x-2*x^2-2*x^3). %H A077981 G. C. Greubel, Table of n, a(n) for n = 0..1000 %H A077981 Index entries for linear recurrences with constant coefficients, signature (-2,2,2). %F A077981 a(n) = (-1)^n * A077937(n). - _Ivan Neretin_, Jun 19 2015 %t A077981 LinearRecurrence[{-2,2,2}, {1,-2,6}, 30] (* or *) CoefficientList[ Series[1/(1+2*x-2*x^2-2*x^3), {x,0,30}], x] (* _G. C. Greubel_, Jun 25 2019 *) %o A077981 (PARI) Vec(1/(1+2*x-2*x^2-2*x^3) + O(x^30)) \\ _Michel Marcus_, Jun 19 2015 %o A077981 (Magma) R:=PowerSeriesRing(Integers(), 30); Coefficients(R!( 1/(1+2*x-2*x^2-2*x^3) )); // _G. C. Greubel_, Jun 25 2019 %o A077981 (Sage) (1/(1+2*x-2*x^2-2*x^3)).series(x, 30).coefficients(x, sparse=False) # _G. C. Greubel_, Jun 25 2019 %o A077981 (GAP) a:=[1,-2,6];; for n in [4..30] do a[n]:=-2*a[n-1]+2*a[n-2]+ 2*a[n-3]; od; a; # _G. C. Greubel_, Jun 25 2019 %Y A077981 Cf. A077937. %K A077981 sign,easy %O A077981 0,2 %A A077981 _N. J. A. Sloane_, Nov 17 2002 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE