Conjecture for even quadratic-polynomial values in the square-free real quadratic case

From papers

Let d2(mod4)d\equiv 2\pmod 4 be a positive square-free integer. Define

Meven(d)=max{ω(dx2):2xd, x even}.M'_{\mathrm{even}}(d)=\max\{\omega(d-x^2):2\leq x\leq\sqrt d,\ x\text{ even}\}.

Conjecture. Meven(d)2M'_{\mathrm{even}}(d)\leq 2 if and only if d{2,6,10,14,22,26,30,38,42,62,110,122,182,278,362,398}d\in\{2,6,10,14,22,26,30,38,42,62,110,122,182,278,362,398\}.

The claim concerns an unresolved real-quadratic analogue of the preceding factorization problems. The source says that it is suggested by easy numerical computations and that no finiteness result is currently available because the needed smallness of the fundamental unit has not been proved.

Progress summary

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Sources & referencesView supporting material

Primary source

Stéphane Louboutin, “Ideal class groups of some quadratic number fields and factorization of values of some quadratic polynomials”, arXiv:2511.15243 (2025).

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