The problem description is here, and click here to see all my other Euler solutions in F#.
This is a more difficult version of problem 82, and now you can move in all four directions!
This is a more difficult version of problem 81, but still, as you can’t move left so we can still optimize one column at a time.
After reading the question, a quick search on how to test if a point is in a triangle turned up this useful SO answer. Translating the algorithm to…
I based my solution on Euclid’s formula for generating Pythagorean triples.
Consider the following “magic” 3-gon ring, filled with the numbers 1 to 6, and each line adding to nine.
The primes 3, 7, 109, and 673, are quite remarkable. By taking any two primes and concatenating them in any order the result will always be prime. For example, taking 7 and 109, both 7109 and 1097 are prime. The sum of these…