Asymptotic bounds for the number of convex n-ominoes

Unit squares having their vertices at integer points in the Cartesian plane are called cells. A point set equal to a union of n distinct cells which is connected and has no finite cut set is called an n-omino. Two n-ominoes are considered the same if one is mapped onto the other by some translation of the plane. An n-omino is convex if all cells in a row or column form a connected strip. Letting c(n) denote the number of different convex n-ominoes, we show that the sequence ((c(n))^1^n: n=1,2,...) tends to a limit @c and @c=2.309138....