Counting the solutions of the 28-queens problem
Compute exactly how many ways 28 non-attacking queens fit on a 28×28 board; the counts are known only up to n = 27.
Problems
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Matching problems
MIPLIB 2017 instances with no known feasible solution
Find any feasible point, or prove infeasibility, for the six MIPLIB 2017 instances with no known solution, including Eternity II.
Counting Langford pairings for 31 and 32 pairs
Compute the exact number of Langford pairings of order 31 and 32, estimated near 5×10^24 and 9×10^25; counts are known up to order 28.