A stable Grothendieck polynomial 
is the symmetric formal power series
 |
where 
ranges over set-valued semistandard Young tableaux
of shape 
.
Each box contains a nonempty finite set of positive
integers, with the largest entry in a box at most the smallest entry in the next
box in its row and strictly less than the smallest entry in the box below it. Here
counts entries, 
counts boxes, and 
is the product of the variables indexed by all entries (Buch
2002). In finitely many variables, its lowest-degree homogeneous component is the
Schur polynomial 
.
For partitions 
, define their join and meet componentwise by 
and 
.
Guo et al. (2026) proved the Thomas-Yong conjecture (Thomas and Yong 2009)
that
 |
where every 
is a nonnegative integer. Guo
et al. (2026) report that ChatGPT supplied the main proof
strategy.
