A192440 Coefficient of x^floor(n/2) in the expansion of (1+x+x^3)^n.

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

Offset

0,3

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Prog

(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

Crossrefs

Cf. A002426.

Sequence in context: A298537 A272079 A212606 * A327711 A274964 A054357

Adjacent sequences: A192437 A192438 A192439 * A192441 A192442 A192443

Keyword

nonn

Author

Joerg Arndt, Jul 01 2011

Status

approved