@sushmita comment,
for even numbers- 1.5n-2
for odd- 3/2(n-1) Comparisons
it basically keeps you away from fraction and give positive integers (positive whole numbers) .
any even number multiply with .5 give whole number always.
now, for even – 1.5n making whole number
and in odd – (n-1) making it even and even multiply with 1.5 give whole number.