Aglaia's Cliffs of Arithmetic

Huge cliffs, jutting out into the raging sea. You can climb down them, but you have to use your brain, for the combination is hidden within the ivory rocks. 2 by 4 and 8 by 2, square it, 3 and 4, long and short. Jump 5 times and turn the right. N to the fifth power, and C times nine, the goddess here can do just fine.