As suggested by David Verrelli on 15-Dec-2017, I have edited the problem statement to reconcile it with the test suite. For everyone's reference, the original problem statement was:
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the primes below the input, N.
But that problem statement didn't match one of the test suite cases.
Since I didn't change the test suite, the solutions did not need to be rescored.
Thanks for Cris for pointing out a hole in my original test suite. I added a test case that has a removable vertex as the first row of P and rescored all entries.
This is the second time I've gotten up in the middle of the night to try to fix this. ;-) In my previous attempt to fix test case 7, I was fooled by the diagram I drew.
I've modified test case 7 again. When I run your latest solution, Cris, it passes. We'll see what happens when the solutions all get rescored again.
Hey guys ... Don't worry, I'm not going to mess with you by adding new test cases that are subject floating-point round-off error. This will be in interesting point to discuss when I post a follow-up on my blog.