寻求递推公式：当n=1时m=1,n=2时m=3,n=3 m=5,n=4 m=8,n=5 m=11,n=6 m=15,n=

m = Pn + c
P = (m2 - m1)/(n2 - n1)
= (3 - 1)/(2 - 1)
= 2
m = 2n + c
n = 3,m = 5
5 = 2(3) + c
c = -1
m = 2n - 1