There is a RAND (type "=RAND") function that you can use. It gives a random number between 0 and 1. Scale and shift this number to give you the 1 - 16 range. Use the ROUND, ROUNDUP or ROUNDDOWN functions to condition the scaled number.
You will also need to recalculate the spreadsheet to generate the next set of numbers.
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"Reason is not automatic. Those who deny it cannot be conquered by it. Do not count on them. Leave them alone." - Ayn Rand