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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 (list; graph; refs; listen; history; text; internal format)
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.

LINKS

Table of n, a(n) for n=1..17.

FORMULA

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

CROSSREFS

Sequence in context: A229443 A335769 A139026 * A181207 A068315 A069586

Adjacent sequences:  A135939 A135940 A135941 * A135943 A135944 A135945

KEYWORD

hard,more,nonn

AUTHOR

Tanya Khovanova, Mar 03 2008

EXTENSIONS

More terms from Joerg Arndt, May 21 2018

STATUS

approved

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Last modified August 4 08:20 EDT 2020. Contains 336201 sequences. (Running on oeis4.)