We introduce a generating-function framework for analyzing the no-feedback card-guessing game after $ k $ Gilbert–Shannon–Reeds riffle shuffles. We show that the distribution of the card appearing in position $ i $ can be expressed as a structured mixture of $ 2^k $ tractable components, each corresponding to a sum of independent Bernoulli trials. From this decomposition, we derive an explicit closed-form expression for the probability generating function, represented as a product of binomial-type polynomials with a clear and systematic structure, valid for any number of cards $ n $ and any number of shuffles $ k $. This formulation replaces recursive convolutions with a single analytic expression, enabling efficient computation and revealing the combinatorial–probabilistic structure underlying riffle shuffles. Beyond exact evaluation, the framework connects optimal no-feedback strategies with the generating functions and suggests asymptotic behavior in both the fixed-$ k $, large-$ n $ and fixed-$ n $, large-$ k $ regimes.
Citation: Tipaluck Krityakierne, Thotsaporn Aek Thanatipanonda. A generating function framework for the no-feedback card guessing game after riffle shuffles[J]. AIMS Mathematics, 2025, 10(10): 24257-24269. doi: 10.3934/math.20251075
We introduce a generating-function framework for analyzing the no-feedback card-guessing game after $ k $ Gilbert–Shannon–Reeds riffle shuffles. We show that the distribution of the card appearing in position $ i $ can be expressed as a structured mixture of $ 2^k $ tractable components, each corresponding to a sum of independent Bernoulli trials. From this decomposition, we derive an explicit closed-form expression for the probability generating function, represented as a product of binomial-type polynomials with a clear and systematic structure, valid for any number of cards $ n $ and any number of shuffles $ k $. This formulation replaces recursive convolutions with a single analytic expression, enabling efficient computation and revealing the combinatorial–probabilistic structure underlying riffle shuffles. Beyond exact evaluation, the framework connects optimal no-feedback strategies with the generating functions and suggests asymptotic behavior in both the fixed-$ k $, large-$ n $ and fixed-$ n $, large-$ k $ regimes.
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