Corner's of Ulam Spiral
- The corners of the Ulam Spiral are
4n^2+2n+1 (SW) and
4n^2-4n+2 (SE) [this is always divisible by 2]
The first one produces good primes, and the line parallel to it
4n^2-2n-1 produces even more
11, 29, (55), 89, 131, 181, 239, ...
Milton L. Brown