A236584 The number of tilings of a 9 X (2n) floor with 2 X 3 hexominoes.

1, 1, 1, 5, 11, 19, 45, 105, 219, 475, 1061, 2313, 5027, 11035, 24173, 52793, 115499, 252827, 552981, 1209545, 2646419, 5789563, 12664925, 27706873, 60614235, 132602171, 290087749, 634616521, 1388325507, 3037181147

Offset: 0

Author

R. J. Mathar, Jan 29 2014

Keywords

• easy
• nonn

Comments

Tilings are counted irrespective of internal symmetry: Tilings that match each other after rotations and/or reflections are counted with their multiplicity.

Links

• R. J. Mathar, Paving rectangular regions..., arXiv:1311.6135, Table 52.
• R. J. Mathar, Tilings of Rectangular Regions by Rectangular Tiles: Counts Derived from Transfer Matrices, arXiv:1406.7788 [math.CO], eq. (35).
• Index entries for linear recurrences with constant coefficients, signature (2,-1,4,-2).

Crossrefs

Cf. A000079 (5Xn floor), A182097 (6Xn floor), A000244 (7Xn floor), A236583 (8X3n floor)

Programs

Maple

g := (1-x)/(-4*x^3+1-2*x+x^2+2*x^4) ;
taylor(%,x=0,30) ;
gfun[seriestolist](%) ;

Formula

G.f.: (1-x)/(-4*x^3+1-2*x+x^2+2*x^4).