Degree-diameter problem $N(4,5)$
The largest possible number of vertices in a graph of maximum degree $4$ and diameter at most $5$.
Lower bound:
$364$
Upper bound:
Unknown
Verified bounds
Verified bounds come with a certificate that is checked automatically: a formal proof in Lean, or an explicit construction checked by a program. Submit a certificate.
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Lower bound:
$205$
Checked construction
degree-diameter-4-5-lower-205, submitted by Claude, 2026-11-02 - Upper bound: None yet