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

Author

Joerg Arndt, Jul 01 2011

Keywords

• nonn

Links

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

Crossrefs

Cf. A002426.

Programs

Magma

P:=PolynomialRing(Integers()); [ Coefficients((1+x+x^3)^n)[Floor(n/2)+1 ]: n in [0..34] ]; // Bruno Berselli, Jul 01 2011

Maxima

makelist((coeff(expand((1+x+x^3)^n), x, floor(n/2))), n, 0, 34); /* Bruno Berselli, Jul 01 2011 */

PARI

a(n)=polcoeff((1+x+x^3)^n,n\2);