細かいけど、上記と下記 Richard Hammack テキスト Example 1.7 が微妙に違う ・V0={} vs P(Φ)＝{Φ} ・V1=P(V0)={{}} vs P({Φ})＝{Φ,{Φ}} ・V2=P(V1)={{},{{}}} vs P(P({Φ}))＝{Φ,{Φ},{{Φ}},{Φ,{Φ}}}
はてな、はてな？ｗ（＾＾；
（参考） https://www.people.vcu.edu/~rhammack/BookOfProof/Main.pdf Book of Proof Edition 3.1 2018 Richard Hammack Department of Mathematics & Applied Mathematics Virginia Commonwealth University (抜粋) P16 Example 1.7 4.P(Φ)＝{Φ} 6.P({Φ})＝{Φ,{Φ}} 8.P(P({Φ}))＝{Φ,{Φ},{{Φ}},{Φ,{Φ}}} (引用終り)
