Sum-free sets generated by the period-k-folding sequences and some Sturmian sequences

First, we show that the sum-free set generated by the period-doubling sequence is not $\kappa$-regular for any $\kappa \ge 2$. Next, we introduce a generalization of the period-doubling sequence, which we call the period-$k$-folding sequences. We show that the sum-free sets generated by the period-$k$-folding sequences also fail to be $\kappa$-regular for all $\kappa \ge 2$. Finally, we study the sum-free sets generated by Sturmian sequences that begin with `11’, and their difference sequences.