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A192440
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Coefficient of x^floor(n/2) in the expansion of (1+x+x^3)^n.
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3
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1, 1, 2, 3, 6, 10, 26, 42, 126, 198, 612, 957, 2970, 4654, 14534, 22815, 71838, 112846, 357884, 562343, 1793296, 2818536, 9026976, 14191575, 45612450, 71726650, 231224060, 363685545, 1175422590, 1849145850, 5989693176, 9424458831, 30586693182, 48133936158, 156483812892
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OFFSET
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0,3
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..200
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PROG
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(PARI) a(n)=polcoeff((1+x+x^3)^n, n\2);
(Maxima) makelist((coeff(expand((1+x+x^3)^n), x, floor(n/2))), n, 0, 34); /* Bruno Berselli, Jul 01 2011 */
(Magma) P<x>:=PolynomialRing(Integers()); [ Coefficients((1+x+x^3)^n)[Floor(n/2)+1 ]: n in [0..34] ]; // Bruno Berselli, Jul 01 2011
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CROSSREFS
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Cf. A002426.
Sequence in context: A298537 A272079 A212606 * A327711 A274964 A054357
Adjacent sequences: A192437 A192438 A192439 * A192441 A192442 A192443
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KEYWORD
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nonn,changed
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AUTHOR
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Joerg Arndt, Jul 01 2011
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STATUS
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approved
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