Constrained A region-count formula

Determine the exact maximum number of regions formed by n constrained long-legged A shapes, including whether the experimentally suggested formula a_{\overline{\sf A}}(n) = floor(10n²/3) holds for n > 0.

Background

A constrained long-legged A is a long-legged A whose crossbar endpoints are equidistant from its tip, considered up to similarities. Two copies can intersect in at most eight points, giving the general upper bound a_{\overline{A}}(n) ≤ 4n² − 2n + 1.

Computer searches found values 1, 3, 13, 30, 53, and 83 for n from 0 through 5, suggesting the sequence floor(10n²/3) for positive n. However, the authors emphasize that numerical precision issues and very small regions make even this proposed formula uncertain.

References

Nonetheless, we are not at all sure that even this formula is correct.

Cutting a Pancake with an Exotic Knife  (2511.15864 - Cutler et al., 19 Nov 2025) in Section 7.2, following equation (EqcA2)