Try find the billionth fibonacci number. The answer should be in hexadecimal, and to prove that you have the whole number, you need to post the first 10 bytes and the last 10 bytes. I solved it in 2500 seconds on an 8-core machine. Winner will get special mention.
What is the largest double that could in theory be produced by Math.random()? In this newsletter, we look at ways to calculate this based on the 48-bit random generator available in standard Java. We also prove why in a single-threaded program, (int)(Random.nextDouble() + 1) can never be rounded up to 2.