ZarankiewiczDB,

an online database of Zarankiewicz numbers.

z(20,21) = 100

By deleting 1 row from the finite projective plane of order 4.

lower bound = 100, submitted on April 22nd, 2016 (link)

By Roman's bound with $p = 4$. [Rom75]

upper bound = 100, submitted on April 22nd, 2016 (link)

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