For all natural values of n, 𝑛(𝑛² − 1) is

n(n² − 1) = 𝑛(𝑛 + 1)(𝑛 − 1)
𝑛 − 1, 𝑛, 𝑛 + 1 are three consecutive natural numbers we have product of 3 consecutive
natural numbers are always divisible by 2 and 3.
⇒ 𝑛(n²− 1)   is a multiple of '6