A239658 - OEIS

%I #29 May 22 2022 16:43:42

%S 1,1,3,11,75,528,4584,40609,373981,3493723,33079702,316109657,

%T 3044648053

%N Number of free triangular n-polyplets (triangular polyominoes connected at edges or corners),  where turning over is allowed and holes are allowed.

%C 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.

%Y Cf. A000577, A030222.

%K nonn,hard,more

%O 0,3

%A _Abe Wits_ and Ragnar Groot Koerkamp, Nov 20 2020

%E a(11) and a(12) from _Aaron N. Siegel_, May 22 2022