A390620 Number of free polynars with n cells.

1, 2, 9, 60, 467, 4226, 39972, 390903, 3886181, 39154600, 398364048, 4086060896

Offset

1,2

Comments

A polynar is like a polyomino, but the cells can be joined either along a full edge or along a half edge.

According to Sicherman (see link), polynars were first studied by László Molnár.

Links

Table of n, a(n) for n=1..12.

George Sicherman, Catalogue of Polynars.

Index entries for sequences related to polyominoes.

Crossrefs

Cf. A000105, A390621 (one-sided), A390622 (fixed).

Sequence in context: A156272 A366240 A363390 * A381778 A205570 A381300

Adjacent sequences: A390617 A390618 A390619 * A390621 A390622 A390623

Keyword

nonn,more

Author

Pontus von Brömssen, Nov 14 2025

Extensions

a(10)-a(11) from Christian Sievers, Nov 15 2025

a(12) from John Mason, Jan 30 2026

Status

approved