Reciprocal

1/a(n+ 1)= 1/an+ 1/2

1/a 1= 1

{1/an} is a arithmetic progression with 1 as the first term and 1/2 as the tolerance.

1/an = 1+( 1/2)*(n- 1)

1/an=(n+ 1)/2

an=2/(n+ 1)