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A077977
Expansion of 1/(1+x+2*x^2-2*x^3).
4
1, -1, -1, 5, -5, -7, 27, -23, -45, 145, -101, -279, 771, -415, -1685, 4057, -1517, -9967, 21115, -4215, -57949, 108609, -1141, -331975, 551475, 110193, -1877093, 2759657, 1214915, -10488415, 13577899, 9828761, -57961389, 65459665, 70120635, -316962743, 307640803, 466525953
OFFSET
0,4
FORMULA
a(n) = (-1)^n * A077956(n). - G. C. Greubel, Jun 25 2019
MATHEMATICA
LinearRecurrence[{-1, -2, 2}, {1, -1, -1}, 50] (* Vincenzo Librandi, Sep 09 2016 *)
PROG
(Magma) I:=[1, -1, -1]; [n le 3 select I[n] else -Self(n-1)-2*Self(n-2)+2*Self(n-3): n in [1..50]]; // Vincenzo Librandi, Sep 09 2016
(PARI) Vec(1/(1+x+2*x^2-2*x^3) + O(x^50)) \\ Michel Marcus, Sep 09 2016
(Sage) (1/(1+x+2*x^2-2*x^3)).series(x, 50).coefficients(x, sparse=False) # G. C. Greubel, Jun 25 2019
(GAP) a:=[1, -1, -1];; for n in [4..50] do a[n]:=-a[n-1]-2*a[n-2]+2*a[n-3]; od; a; # G. C. Greubel, Jun 25 2019
CROSSREFS
Cf. A077956.
Sequence in context: A006146 A284129 A077956 * A019204 A301733 A114367
KEYWORD
sign,easy
AUTHOR
N. J. A. Sloane, Nov 17 2002
STATUS
approved