%I #14 Jan 04 2023 11:55:00
%S 1,1,2,5,12,35,108,368,1283,4639,17003,63222,236819,893515,3387953,
%T 12904855,49335965,189243115
%N Number of free polyominoes with n cells having simply-connected interiors.
%C The polyominoes referred to in the definition are those having a single traceable perimeter. The definition therefore includes the heptomino with a hole, as in this case the border, although not self-avoiding (it meets itself at a corner) is still traceable; it excludes the square octomino with a hole, whose border consists of two distinct polygons. Thus starting from n=8, A000104(n) < a(n) < A000105(n).
%Y Cf. A000104 (free polyominoes without holes), A000105 (free polyominoes).
%K nonn,more
%O 1,3
%A _John Mason_, _Allan C. Wechsler_, Mar 15 2021
%E a(17)-a(18) from _John Mason_, Jan 04 2023