OFFSET
1,8
LINKS
D. H. Redelmeier, Counting polyominoes: yet another attack, Discrete Math., 36 (1981), 191-203.
EXAMPLE
a(7)=1 because of:
OOOO
O..OO
OO..O
.OOOO
CROSSREFS
KEYWORD
nonn,more
AUTHOR
John Mason, Oct 18 2021
STATUS
approved