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A239658
Number of free triangular n-polyplets (triangular polyominoes connected at edges or corners), where turning over is allowed and holes are allowed.
1
1, 1, 3, 11, 75, 528, 4584, 40609, 373981, 3493723, 33079702, 316109657, 3044648053
OFFSET
0,3
COMMENTS
We get triangular polyominoes when connecting over edges only (rather than edges and corners); that is A000577. The square equivalent (that is, n-polyplets) is A030222. The neighborhood is also known as the Triangular Moore neighborhood, and equals the moves of the Tri-Chess king.
CROSSREFS
Sequence in context: A374533 A203772 A290025 * A181388 A196691 A197064
KEYWORD
nonn,hard,more
AUTHOR
Abe Wits and Ragnar Groot Koerkamp, Nov 20 2020
EXTENSIONS
a(11) and a(12) from Aaron N. Siegel, May 22 2022
STATUS
approved