%I #9 Dec 13 2023 04:03:52

%S 1,1,2,3,8,13,36,76,202,482,1281,3277,8749,23083,62056,166498,450576,

%T 1220542,3321870,9057388,24769906

%N Number of perforated polyominoes with n cells, identifying mirror images.

%C A perforated polyomino is a polyomino in which every cell has at least one even coordinate.

%e a(4)=3 because there are 5 tetrominoes, and the skew and square tetrominoes do not lie in the perforated grid, which leaves 3.

%Y Cf. A000105, number of polyominoes with n cells; A292065, number of Besźel Polycubes with n cells, distinguishing mirror images; A292157, same but identifying mirror images.

%K nonn,more,hard

%O 1,3

%A _George Sicherman_, Oct 23 2017

%E a(16) - a(21) from _Joerg Arndt_, Dec 11 2023