login
A135942
Number of n-celled polyominoes with perimeter < 2n+2.
0
0, 0, 0, 1, 1, 8, 25, 114, 438, 1826, 7339, 29876, 120346, 485155, 1947974, 7812084, 31267765
OFFSET
1,6
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).
CROSSREFS
Sequence in context: A229443 A335769 A139026 * A181207 A068315 A069586
KEYWORD
hard,more,nonn
AUTHOR
Tanya Khovanova, Mar 03 2008
EXTENSIONS
More terms from Joerg Arndt, May 21 2018
STATUS
approved