Given a set S of words, let \(S^\dagger \) denote the iterated shuffle of S. We characterize the finite sets S for which \(S^\dagger \) is co-finite, and we give some bounds on the length of a longest word not in \(S^\dagger \).
['Jeremy Nicholson', 'Narad Rampersad']
The Frobenius problem for the shuffle operation