Project Euler #58: Primes along the diagonals of a square spiral
A bit of math

It is interesting to see that the corners of a square of size \$s\$ have values: \$s^2-3s+3\$, \$s^2-2s+2\$, \$s^2-s+1\$, \$s^2\$. (Also \$s^2\$ is not a prime ;-))

To be continued later.