a 1= 1

a2=3/4

a3=3/5

a4= 1/2

a5=3/8

It is known that:

a(n+ 1) / an = (n+2) / (n+3)

Therefore:

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

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

......

a3 / a2 = 4/5

a2 / a 1 = 3/4

Multiply both sides of the above formula:

a(n+ 1) / a 1 = 3/(n+3)

Therefore:

a(n+ 1) = 3/(n+3)

So:

an = 3/(n+2)