$18^2 = 18 * 18 = 324$;
$5^3 = 5 * 5 * 5 = 125$;
$13^2 = 13 * 13 = 169$;
$20^3 = 20 * 20 * 20 = 400 * 20 = 8000$;
$40^2 = 40 * 40 = 1600$;
$30^3 = 30 * 30 * 30 = 900 * 30 = 27000$.