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Number of free linear polycubes of size n, identifying rotations and reflections and avoiding neighbors at [0,0,+-2], [0,+-2,0], and [+-2,0,0].
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%I #9 May 21 2023 12:56:39

%S 1,1,1,2,4,9,20,51,128,338,882,2350,6238,16693,44561,119339,319104,

%T 854420,2285357

%N Number of free linear polycubes of size n, identifying rotations and reflections and avoiding neighbors at [0,0,+-2], [0,+-2,0], and [+-2,0,0].

%C Linear polycubes have two end points with one neighbor, the remaining cubes all have two neighbors.

%C When a cube [x,y,z] is in the polycube then neither of the six cubes [x+-2,y,z], [x,y+-2,z], [x,y,z+-2] can be in the polycube. For example, no three cubes can be in a row.

%Y Cf. A363204 (linear and avoiding at [+-1,+-1,+-1]).

%K nonn,more

%O 1,4

%A _Joerg Arndt_ and _Márk Péter Légrádi_, May 21 2023