248025domain: NAppears in sequencesa(n) = Sum_{k=0..n} T(n,k) * T(n,2n-k), with T given by A027023.at n=10A027041Number of sets of nonempty words with a total of n letters over binary alphabet such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter.at n=17A293741