Exact Saturation and Independent Domination Numbers of Prism Graphs

We determine exactly the saturation number and independent domination number of every prism graph Y_n = C_n square K_2. For all n >= 3, the saturation number is ceil(2n/3), while the independent domination number is given by an explicit formula depending on n modulo 4. Consequently, the TxGraffiti regular saturation inequality i(Y_n) <= mu*(Y_n) holds throughout the prism family, with equality exactly for n in {3,5,6,9}. The proofs are self-contained. Independent finite-state dynamic programs verify both formulas through n = 200, and a separate exhaustive cyclic-word computation checks the independent-domination formula through n = 14. This record proves the inequality only for prism graphs and does not claim to settle the general conjecture.