OFFSET
1,6
LINKS
D. H. Redelmeier, Counting polyominoes: yet another attack, Discrete Math., 36 (1981), 191-203.
EXAMPLE
a(2)=1 because of:
OO
OO
a(4)=1 because of:
OOO
O.O
OOO
a(5)=1 because of:
OOOO
O..O
OOOO
CROSSREFS
KEYWORD
nonn,more
AUTHOR
John Mason, Oct 18 2021
STATUS
approved