A380990 Number of free polyominoes with n cells with at most 4 collinear cell centers on any line in the plane.
1, 1, 2, 5, 11, 31, 85, 262, 764, 2255, 6341, 17221, 43994, 106205, 239367, 502611, 977791, 1771624, 2989373, 4687803, 6819069, 9234529, 11622453, 13527854, 14571011, 14643347, 13747913, 12041014, 9905945, 7763985, 5805906, 4139266, 2858796, 1971455, 1368967, 942226, 618148, 368480, 186275, 73649, 20236, 3476, 400, 96, 27, 12, 2, 1
Offset: 1
Links
- Dave Budd, python code
Programs
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Python
# See links
Formula
a(n) = Sum_{k=1..4} A377942(n,k).