BUILD-HEAP(A)
 heap-size[A] ← length[A]
  for i ← length[A]/2 downto 1
   do HEAPIFY(A, i)

lg n                     lg n
∑ n/(2^h+1)*O(h)  = O(n* ∑ O(h/2^h))
h=0                      h=0

∞
∑ k*x^k = X/(1-x)^2
k=0
               ∞
Putting x=1/2, ∑h/2^h = (1/2) / (1-1/2)^2 = 2
               h=0

lg n                     ∞
O(n* ∑ O(h/2^h))  = O(n* ∑ O(h/2^h))  = O(n)
h=0                      h=0