What is the maximum number of doughnuts that cannot be ordered using combinations...?

[Ilikebugs]

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“Baker’s Dozen Doughnut Shop” doughnuts are sold only in boxes of 7, 13, or 25. To buy 14 doughnuts you must order two boxes of 7, but you cannot buy exactly 15 doughnuts since no combination of boxes contains 15 doughnuts.


What is the maximum number of doughnuts that cannot be ordered using combinations of the three different size boxes from “Baker’s Dozen Doughnut Shop”?

I know it's the frobenius number but I don't know how to solve it

 

[Otis]

“Baker’s Dozen Doughnut Shop” doughnuts are sold only in boxes of 7, 13, or 25. To buy 14 doughnuts you must order two boxes of 7, but you cannot buy exactly 15 doughnuts since no combination of boxes contains 15 doughnuts.


What is the maximum number of doughnuts that cannot be ordered using combinations of the three different size boxes from “Baker’s Dozen Doughnut Shop”?

I know it's the frobenius number but I don't know how to solve it

Check out this article, to start your research:

https://en.wikipedia.org/wiki/Coin_problem

It appears that there's no direct formula for three denominations, but they discuss an algorithm for finding the Frobenius Number in your case.