Solution: According to the meaning of the question, figure 1 has 1 number forks, figure 2 has 3 tree forks, figure 3 has 8 tree forks, and figure 4 has 18 tree forks. The law is an+1-an = n 2+1,where An+65438. The number in figure 7 is an+1-an = N2+1a6+1-a6 = a7-a6 = 6 2+1= 36+1= 37.