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

1,3

Comments

Image of the last in the sequence (n=48). This being the largest polyomino with at most 4 collinear cell centers on any line in the plane.

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Links

Table of n, a(n) for n=1..48.

Dave Budd, Python code.

Hugo van der Sanden, C code.

Formula

a(n) = Sum_{k=1..4} A377942(n,k).

Prog

(Python) # See links.
(C) // See links.

Crossrefs

Cf. A000105, A377942, A378169.

Sequence in context: A139467 A124481 A002862 * A190865 A275427 A139464

Adjacent sequences: A380987 A380988 A380989 * A380991 A380992 A380993

Keyword

nonn,fini,full,nice

Author

Dave Budd, Feb 11 2025

Extensions

All terms verified by Hugo van der Sanden, Feb 08 2026

Status

approved