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            | Abstract |  
            | We prove two integral transformations that relate different constructions of rational approximations
 to .
 The first one relates a double integral over the unit square and a Barnes-type
 integral. The second one relates two Barnes-type integrals and was discovered and
 proved by W. Zudilin using an automated proof method. Here we offer a proof based
 on more classical means such as contiguous relations, the second Barnes lemma and
 the duplication formula for the gamma function.
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            | To the memory of Naum Ilyitch Feldman
              (1918–1994) |  
    
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            | Keywords
                Legendre polynomials, irrationality measure, zeta values,
                hypergeometric functions, human-generated proofs
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            | Mathematical Subject Classification 2010
                Primary: 11J82
               
                Secondary: 33C20, 33C60
               |  
          
            | Milestones
                Received: 31 December 2019
               
                Accepted: 5 May 2020
               
                Published: 5 November 2020
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