Contents

Russian Mathematics

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Vol. 70, No. 4, 2026

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(s,t)-Fermat, (s,t)-Fermat–Lucas Sequences and Their Applications on Hyperbolic Quaternions

H. Akkuş and E. Özkan p. 1  abstract

Monomial Rota–Baxter Operators of Weight Zero and Averaging Operators on the Polynomial Algebra

A. Khodzitskii p. 21  abstract

A Problem with a Shift Condition on Internal Characteristics for One Class of Mixed-Type Equations with Different Orders of Degeneration

M. Mirsaburov and A. K. Makhmudov p. 42  abstract

On Periodic Solutions of a System of Nonlinear Ordinary Second-Order Differential Equations

E. Mukhamadiev and A.N. Naimov p. 56  abstract

Dynamic Stresses near a Supported Cylindrical Rupture Surface During under Harmonic Wave

B. Sh. Usmonov, B. Z. Nuriddinov, and J. Z. Nuriddinov p. 63  abstract

Functors between C*-Relations

K. A. Shishkin p. 72  abstract

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