A056883 - OEIS

%I #18 Oct 11 2022 07:00:11

%S 0,0,0,1,1,5,4,18,19,72,72,268,276,1002,1043,3733,3926,14000,14810,

%T 52658,55987,199020,212364,754826,807861,2872926,3082202,10966333,

%U 11789248,41970489,45198317,160996986,173640109,618839771,668316169,2383000591,2576516523,9191269314,9947949563,35502661446

%N Number of n-celled rotationally symmetric polyominoes without holes.

%C In other words, free unholey polyominoes with 180-degree rotational symmetry and no other. - _John Mason_, Oct 11 2022

%H Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/animals.html">Enumeration of polyominoes</a>

%Y Cf. A000104, A006747 (with holes allowed).

%K nonn

%O 1,6

%A _N. J. A. Sloane_, Sep 03 2000

%E a(29)-a(40) from _John Mason_, Oct 11 2022