counting stable sets recursively...need help

Given a linked list tree, where A is the root, with 2 children B and C. And B has two children D and E, such that A->[B->C] C->[D->E] . In this case, there are 14 stable sets. A stable set is a possibly empty subset, S, of the vertices such that no two nodes in S are adjacent to each other in the tree.

How would I use recursion to count the stable sets of the tree?

public int StableSets()

{

ListNode child = children;

TreeNode tree = null;

while(child != null)

{

count++;

tree = (TreeNode) child.getData();

if (t!=null){

c += tree.StableSets();

if (child.getNext() != null){

}

}

child = child.getNext();

}

return c;

}