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4. (24 pts) In combinatorial mathematics, the Catalan numbers form a sequence of natural numbers that satisfy the recursive relation where n and i are integers. The Catalan numbers for 0, 1, 2, 3, 4, and 5 are respectively 1, 1, 2, 5, 14, and 42 Complete the four missing or incomplete lines of the function CatR, which computes the nth Catalan number Cn using the recursive relation in Eq. (2) begin code 1 function C CatR(n) 2 | % Computes the nth Catalan number Cn % n is a non-negative integer if %Base case 1 else % Initialization for % Iteration 21 end as end end code