  An open partition \pi{} [Cod09a, Cod09b] of a tree T is a partition of the
vertices of T with the property that, for each block B of \pi, the upset of B
is a union of blocks of \pi. This paper deals with the number, NP(n), of open
partitions of the tree, V_n, made of two chains with n points each, that share
the root.
