OFFSET
3,2
EXAMPLE
a(3) = 1 since the equilateral triangle has no diagonals and therefore one exterior region (with infinite area).
a(4) = 4 since the two diagonals of the square divide the exterior in four regions (with infinite area).
a(5) = 10 since the ten diagonals of the regular pentagon divide the exterior in ten regions (with infinite area) of two different shapes.
CROSSREFS
KEYWORD
nonn
AUTHOR
Martin Renner, Mar 23 2013
STATUS
approved