The whole bounded gap on prime numbers was particularly interesting to me, since we kind of got to see math happen in real time: http://michaelnielsen.org/poly

The whole bounded gap on prime numbers was particularly interesting to me, since we kind of got to see math happen in real time: http://michaelnielsen.org/polymath1/index.php?title=Bounded_gaps_between_primes http://michaelnielsen.org/polymath1/index.php?title=Bounded_... It's neat to be able to see what improvements were thought of and exactly how long it took these mathematicians to think of them.