The first line segment is CA 1, the subscripts are 0 and 1, and the sum is 1, where c comes first, the subscript C =( 1- 1)/2=0, and the subscript a = (1+/kloc).

The second line segment is A 1C 1, and the subscripts are 1 and 1, and the sum is 2, with a in front and a subscript = C subscript = 2/2 =1;

The third line segment is C 1A2, the subscripts are 1 and 2, and the sum is 3, with c in front. The subscript of c =(3- 1)/2= 1, and the subscript of a = (3+1)/2 = 2;

The fourth line segment is A2C2, with subscripts of 2 and 2, and the sum is 4, with A in front, and the subscript of A = subscript of C = 4/2 = 2;

By analogy, when n is odd, the nth line segment is c (n-1)/2a (n+1)/2; Where (n- 1)/2 and (n+ 1)/2 are subscripts.

When n is even, the nth line segment is an/2cn/2; Where n/2 is the subscript.