One great problem, three kinds of immersion

From a story to your own conjecture

Problem stories open curiosity. The problem workshop is the next place, where curiosity becomes a testable idea.

  1. 1 · DiscoverYou are hereMeet the questionLearn when it appeared and why it still holds people’s attention.
  2. 2 · ChallengeTest one caseMake your first observation in five minutes with a drawing, calculation, or colors.
  3. 3 · DevelopBuild on ideasPublish an observation and grow it through comparisons, conjectures, and counterexamples.
Partially solved1846

Twin Prime Conjecture — Are There Infinitely Many Close-Packed Prime Pairs?

Are there infinitely many pairs (p, p+2) where both are prime? The case is included in de Polignac’s 1846 conjecture. In 2013 Yitang Zhang proved the first finite upper bound for infinitely recurring consecutive-prime gaps, without reaching gap two.

Challenge passport
First posed
1846
Time it held mathematicians
180 years open · as of 2026
Starting level
Start now

Test small cases immediately with a drawing, divisors, or colored pencils.

The starting level measures how easily you can understand and test small cases. It is not the difficulty of a complete proof.

Jump to your first five minutes

No formal prize. The post-2013 bounded-gap theorems must be distinguished from the original gap-two conjecture.

See the puzzle visually

70M2013, Zhang Yitao4,680Polymath8600Polymath8246Maynard12Tao + Maynard6refinement2Twin primes (target)

After Zhang announced a gap of 70 million in 2013, the unconditional bound fell to 246 within months. Reaching the final gap of 2 would prove the Twin Prime Conjecture.

Problem statement

Twin primes are pairs (p, p+2) where both are prime. Is the set {p prime : p+2 prime} infinite?

The story of this puzzle

Zhang had worked outside academia after his doctorate, but he had taught at the University of New Hampshire since 1999 when he submitted his paper in 2013. He proved that consecutive-prime gaps below 70 million occur infinitely often. Polymath and independent methods of Maynard and Tao sharply improved and extended bounded-gap results. The unconditional bound 246 is still logically far from the target gap two; numerical improvement alone does not force the twin-prime conjecture.

Try it yourself

Mini challenge

Find the first 100 twin prime pairs starting with (3,5). Up to 100,000 there are 1,224 pairs. Code a search to 1M and plot the distribution.

Beyond MathVoyage

Loading…