For anyone curious, @ 15 min <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=r75X4Vn_E9k" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=r75X4Vn_E9k</a> discusses a recursive sum() and why getrecursionlimit() is there.