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All Random Solved Random Open
OPEN
Is it true that, for $k\geq 2$, \[\mathrm{ex}(n;\{C_{2k-1},C_{2k}\})=(1+o(1))(n/2)^{1+\frac{1}{k}}.\]
A problem of Erdős and Simonovits.

See also [573] and the entry in the graphs problem collection.