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The selected twelve items are 37, 101, 115, 117, 145, 157, 159, 161\u2013163, 165, and 169.<\/jats:p>","DOI":"10.2478\/forma-2025-0012","type":"journal-article","created":{"date-parts":[[2026,1,9]],"date-time":"2026-01-09T16:26:32Z","timestamp":1767975992000},"page":"145-165","source":"Crossref","is-referenced-by-count":0,"title":["Elementary Number Theory Problems. Part XVII"],"prefix":"10.2478","volume":"33","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4565-9082","authenticated-orcid":false,"given":"Artur","family":"Korni\u0142owicz","sequence":"first","affiliation":[{"name":"Faculty of Computer Science , University of Bia\u0142ystok , Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4224-9798","authenticated-orcid":false,"given":"Adam","family":"Naumowicz","sequence":"additional","affiliation":[{"name":"Faculty of Computer Science , University of Bia\u0142ystok , Poland"}]}],"member":"374","published-online":{"date-parts":[[2025,12,31]]},"reference":[{"key":"2026033010152292748_j_forma-2025-0012_ref_001","doi-asserted-by":"crossref","unstructured":"Grzegorz Bancerek. On multiset ordering. Formalized Mathematics, 24(2):95\u2013106, 2016. doi:10.1515\/forma-2016-0008.","DOI":"10.1515\/forma-2016-0008"},{"key":"2026033010152292748_j_forma-2025-0012_ref_002","doi-asserted-by":"crossref","unstructured":"John Horton Conway and R.K. Guy. 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