a(1)=1=1/(3×1-2)
a(2)=1/2=2/4=2/(3×2-2)
a(3)=3/7=3/(3×3-2)
a(4)=2/5=4/10=4/(3×4-2)
a(5)=5/13=5/(3×5-2)
a(n)=n/(3n-2)