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Kourovka Notebook — 21st edition

September 2026 edition. Active sections and the solved archive are indexed separately; active-section membership does not certify current openness. Includes all 150 problems in Issue 21.

1,935 catalogue entries · 0 new problem records · 4 catalogue entries linked to problem records

Catalogue entries can be source pointers, solved items or groups of questions. They are not added to the main problem count. Status reflects the saved source, inspected 2026-09-10.

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