Narrow admissible tuples
A database recording, for each k from 2 to 5000, the narrowest known admissible k-tuple, with its diameter, the full tuple (downloadable as a text file), submission date and submitter; entries proven optimal are marked as such. It originated with the 2013 Polymath8 project on bounded gaps between primes, where narrow admissible tuples convert sieve-theoretic results into explicit prime-gap bounds.