OFFSET
1,3
FORMULA
EXAMPLE
a(3) = 12, since reflections or rotations of
OOO KKK OOO
OKO OKO OKO
OOO OOO OOO generate twelve different coverings.
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Nikolaus Meyberg (Nikolaus.Meyberg(AT)t-online.de), Jul 17 2005
STATUS
approved