### Article

## On trees of bounded degree with maximal number of greatest independent sets

For each n and d, we describe the structure of trees with the maximal possible number of greatest independent sets in the class of n-vertex trees of vertex degree at most d. We show that for all even n an extremal tree is unique but uniqueness may fail for odd n; moreover, for d = 3 and every odd n>6, there are exactly ceil{(n-3)/4} + 1 extremal trees. In the paper, the problem of searching for extremal (n; d)-trees is also considered for 2-caterpillars, i.e., trees in which every vertex lies at distance at most two from some simple path. For each n and d=3,4, we completely reveal all extremal 2-caterpillars on n vertices each of which has degree at most d.