'Thirty' in the Bible

and the men of Ai smite of them about thirty and six men, and pursue them before the gate unto Shebarim, and they smite them in Morad; and the heart of the people is melted, and becometh water.

And Joshua riseth, and all the people of war, to go up to Ai, and Joshua chooseth thirty thousand men, mighty ones of valour, and sendeth them away by night,

The king of Tirzah, one; all the kings are thirty and one.