TOPICS
Search

Bras-Amorós Conjecture


The Bras-Amorós conjecture (Bras-Amorós 2008) asserts that the numbers n_g of numerical semigroups of genus g satisfy

 n_(g+1)>=n_g+n_(g-1)

for g>=1. The weaker monotonicity assertion n_(g+1)>=n_g is also called the weak form of the conjecture (Kaplan 2017).

Liu (2026) reported a computer-assisted proof of the weak form for every g>=0. A partial injection handles all but a specified family of source numerical semigroups. Unused targets are bounded using exact transfer computations for 1<=g<=836 and generating function estimates for g>=837. The finite computations bound relaxed counts rather than enumerating all numerical semigroups through genus 836. GPT-6 Astra and Anthropic Fable 5.1 assisted proof development, computation, and checking. As of Oct. 8, 2026, checks of the stored arithmetic outputs had been repeated, but independent verification of the full proof and regeneration of its coefficient arrays had not been reported (VibeMathed 2026). The stronger Fibonacci number inequality and monotonicity at fixed multiplicity remain open.


See also

Fibonacci Number, Numerical Semigroup

Explore with Wolfram|Alpha

References

Bras-Amorós, M. "Fibonacci-Like Behavior of the Number of Numerical Semigroups of a Given Genus." Semigroup Forum 76, 379-384, 2008. https://doi.org/10.1007/s00233-007-9014-8.Kaplan, N. "Counting Numerical Semigroups." Amer. Math. Monthly 124, 862-875, 2017. https://doi.org/10.4169/amer.math.monthly.124.9.862.Liu, M. "Genus Monotonicity for Numerical Semigroups." Oct. 7, 2026. https://github.com/michaeliu4/bras-amoros-monotonicity/blob/main/manuscript/genus-monotonicity_V1.pdf.VibeMathed. "Bras-Amorós Genus-Monotonicity Conjecture." Oct. 7, 2026. https://vibemathed.com/problem/bras-amoros-genus-monotonicity-conjecture.

Cite this as:

Weisstein, Eric W. "Bras-Amorós Conjecture." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Bras-AmorosConjecture.html

Subject classifications