1,1

The polyomino must be rook-wise connected, and a hole is a collection of rook-wise connected empty cells from which a rook cannot escape. - njas, May 25 2006

Tomas Oliveira e Silva, Animal enumerations on the {4,4} Euclidean tiling

a(1) = 7 from

XX

X X

XXX

Sequence in context: A004235 A004236 A065105 this_sequence A080837 A120687 A053217

Adjacent sequences: A118794 A118795 A118796 this_sequence A118798 A118799 A118800

more,nonn

Frank Adams-Watters (FrankTAW(AT)Netscape.net), May 22 2006