EDB — 26N

Exercises

1. [26N]Prerequisites:[24Z]↺↻,[24S]↺↻,[257]↺↻.

   $\forall n,k\in \mathbb{N}$ if $n\in k$ then $Sn\subseteq k$.

   (Hint: you do not need induction, use that each $n\in \mathbb{N}$ is a transitive set).