Math test could earn collectors a profit

Have you ever done the math puzzles where a series of numbers are laid out and then you are asked what the next number is?

Try it this morning.

The numbers are 106,108, 39,281, 18,730 and 9,503.

What is the next number in the sequence?

The answer is something we would all like to know – at least those of us who are following sales of the San Francisco Mint 2018 Silver Reverse Proof Set.

If you can figure out the answer, you will be able to determine whether the set will sell out.

Maximum mintage is 200,000.

All the benefits to speculators that accrue in an instantaneous sellout are out of the question. That boat has sailed.

However, secondary market sellers who eventually can claim they are offering a sold-out product will have an easier time.

But will they be able to?

What the sequence of four numbers represents is the sales increase week to week of the reverse proof set.

First report was 106,108 sold.

The following week, an extra 39,281 were sold.

This put the running total at 145,389.

The next week, an additional 18,730 were sold to bring the running total up to 164,119.

A gain of 9,503 was just reported by the Mint.

The running tally now is 173,622.

What do you think the fifth number in the sequence will be?

My guess is 4,700, roughly half this week’s sales increase, which was also roughly half of the prior week’s increase.

With sales standing at 173,622, adding another 4,700 would leave the set 21,778 short of a sellout.

If the rate of sales keeps dropping by half each week, the set will never sell out.

However, there is another force at work.

When total sales get close enough to a sellout number, there is almost a gravitational pull exerted on buyer behavior to push sales to the sellout number.

Is this week’s 173,622 sales total close enough to have entered that gravity zone?

It is certainly a close call.

My guess of 4,700 additional sales next week would be an indication that gravity has not gone to work.

What do you think?

If you get the answer right, you could earn a profit on the secondary market.

Buzz blogger Dave Harper won the Numismatic Literary Guild Award for Best Blog for the third time in 2017 . He is editor of the weekly newspaper "Numismatic News."