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, 3, 11, 75, 528, 4584, 40609, 373981, 3493723, 33079702, 316109657, 3044648053

Offset: 0

Author

Abe Wits and Ragnar Groot Koerkamp, Nov 20 2020

Keywords

• nonn
• hard
• more

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

Cf. A000577, A030222.

Extensions

a(11) and a(12) from Aaron N. Siegel, May 22 2022