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A059683 Triangle T(n,k) giving number of 3 X k polyominoes with n cells (n >= 3, 1<=k<=n-2). 2
1, 0, 3, 0, 2, 9, 0, 1, 12, 15, 0, 0, 12, 39, 25, 0, 0, 4, 59, 96, 35, 0, 0, 1, 42, 210, 188, 49, 0, 0, 0, 21, 255, 550, 332, 63, 0, 0, 0, 4, 212, 954, 1231, 529, 81, 0, 0, 0, 1, 103, 1184, 2800, 2406, 800, 99, 0, 0, 0, 0, 33, 964, 4634, 6818, 4313, 1142, 121, 0, 0, 0, 0, 6, 546, 5497, 14182, 14722, 7171, 1580 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

3,3

COMMENTS

Note that for k=3 (polyominoes with square bounding rectangle) these are not the free polyominoes, because Read does not apply the full symmetry group of order 8 to reduce the fixed polyominoes for c_q(n), but only the symmetry group of order 4 (excluding the 90 deg rotations). The free polyominoes with square bounding rectangles are the z_3(n) instead. - R. J. Mathar, May 12 2019

LINKS

Table of n, a(n) for n=3..79.

R. C. Read, Contributions to the cell growth problem, Canad. J. Math., 14 (1962), 1-20.

EXAMPLE

Triangle starts:

1;

0,3;

0,2,9;

0,1,12,15;

...

CROSSREFS

Sequence in context: A330646 A099095 A061980 * A030208 A209939 A231101

Adjacent sequences:  A059680 A059681 A059682 * A059684 A059685 A059686

KEYWORD

nonn,easy,nice,tabl

AUTHOR

N. J. A. Sloane, Feb 05 2001

EXTENSIONS

Values for n>=11 cells from R. J. Mathar, May 12 2019

STATUS

approved

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Last modified May 16 22:04 EDT 2021. Contains 343955 sequences. (Running on oeis4.)