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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 (list; graph; refs; listen; history; text; internal format)
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.

LINKS

Table of n, a(n) for n=0..10.

CROSSREFS

Cf. A000577, A030222.

Sequence in context: A342433 A203772 A290025 * A181388 A196691 A197064

Adjacent sequences:  A239655 A239656 A239657 * A239659 A239660 A239661

KEYWORD

nonn,hard,more

AUTHOR

Abe Wits and Ragnar Groot Koerkamp, Nov 20 2020

STATUS

approved

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Last modified July 26 10:35 EDT 2021. Contains 346294 sequences. (Running on oeis4.)