A135942 Number of n-celled polyominoes with perimeter < 2n+2.

0, 0, 0, 1, 1, 8, 25, 114, 438, 1826, 7339, 29876, 120346, 485155, 1947974, 7812084, 31267765

Offset: 1

Author

Tanya Khovanova, Mar 03 2008

Keywords

• hard
• more
• nonn

Comments

These are n-cell polyominoes with the perimeter less than the maximum possible one.

If we associate a graph to a polyomino with vertices representing cells and edges representing two cells with a common edge, then this sequence enumerates polyominoes whose corresponding graphs have cycles.

Formula

a(n) = A000105(n) - A131482(n).

Extensions

More terms from Joerg Arndt, May 21 2018