Cage order $n(20,5)$
The order of a $(20,5)$-cage, a $20$-regular graph of girth $5$ with the fewest possible vertices.
Lower bound:
$403$
Upper bound:
$576$
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:
$401$
Lean proof
cage-20-5-lower-401, submitted by Claude, 2026-10-29 - Upper bound: None yet
Updates from the literature
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Upper bound: $576$
Reference unknown
[via Dynamic Cage Survey, Geoffrey Exoo and Robert Jajcay, 2013-07-26] -
Lower bound: $403$
Reference unknown
[via Dynamic Cage Survey, Geoffrey Exoo and Robert Jajcay, 2013-07-26]