Excess Kurtosis of Pareto Distribution/Lemma 4

Lemma for Excess Kurtosis of Pareto Distribution

 * $3 a^3 \paren {a - 2}^2 \paren {a - 3} \paren {a - 4} = 3 a^7 - 33 a^6 + 132 a^5 - 228 a^4 + 144 a^3$