Depend on the size of the pavers.
144 Get 160 to be safe.
72 Get 80 to be safe.
576 should do it.
216
72 Get 80 to be safe.
264 of them. Get extra for breakage.
78.47 Pavers
Area of 1 paver = 16*16 = 256 square units. Area of patio = 20*20 = 400 square units. Number of pavers required = Area of patio/Area of paver = 400/256 = 1.5625 So 2 pavers will suffice.
One should do it!
272 Get 300 to be safe.
8 x 8 = 64
Area of 1 paver 1 sq ft, area of patio 144 sq ft so 144 pavers.