A set of blocks contains blocks of heights 1, 2, and 4 inches. Imagine constructing towers of piling block of different heights directly on top of one another. Let t(n) be the number of ways to construct a tower of height n inches. Find a recurrence relation for t(1), t(2), t(3)... Here's what I got: There are 5 ways to make a tower of 4 inches, There are 6 ways to make a tower of 5 inches, There are 10 ways to make a tower of 6 inches. t(1) = 1, t(2) = 2, and t(3) = 4 t(k) = t(k-1) + t(k-2) - 1, k >= 4 Is that right? I would guess there should be a t(k-3) in there somewhere just because they give you three numbers.