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A268371
Triangle read by rows: T(n,k) is the number of free polyominoes with width n and height 1<=k<=n.
7
1, 1, 2, 1, 6, 24, 1, 12, 181, 1051, 1, 30, 941, 21992, 238048, 1, 65, 4662, 228013, 9735647, 195284973, 1, 158, 23691, 2337694, 195616247, 15256715219, 577169894573
OFFSET
1,3
COMMENTS
Superset of Craig Knecht's A268311.
LINKS
R. Parkin, L. J. Lander, and D. R. Parkin, Polyomino Enumeration Results, presented at SIAM Fall Meeting, 1967, and accompanying letter from T. J. Lander (annotated scanned copy) page 9 (incorrect at n=15).
EXAMPLE
The first rows of the array are:
1;
1, 2;
1, 6, 24;
1, 12, 181, 1051;
...
T(4,3)=181 = 15+39+59+42+21+4+1: In the 4x3 square fit 15 6-ominoes, 39 7-ominoes, 59 8-ominoes, 42 9-ominoes, 21 10-ominoes, 4 11-ominoes or 1 12-omino. - R. J. Mathar, Jun 07 2020
CROSSREFS
Cf. A268311 (right diagonal), A335711 (column n=2), A000105 (free polyominoes), A292357 (equival. for fixed polys).
Sequence in context: A239740 A375255 A371986 * A318918 A100404 A355005
KEYWORD
nonn,tabl,more
AUTHOR
John Mason, Feb 03 2016
EXTENSIONS
a(16)-a(28) from Jean-Luc Manguin, May 25 2020
STATUS
approved