>>446 補足

これ面白い
下記図で、”The set V5 contains 2^16 = 65536 elements; the set V6 contains 2^65536 elements,”だって
ZFCは、現場の数学では使えない。整数の表現でさえ、爆発していますｗ

https://en.wikipedia.org/wiki/Von_Neumann_universe
Von Neumann universe

In set theory and related branches of mathematics, the von Neumann universe, or von Neumann hierarchy of sets, denoted by V, is the class of hereditary well-founded sets. This collection, which is formalized by Zermelo?Fraenkel set theory (ZFC), is often used to provide an interpretation or motivation of the axioms of ZFC. The concept is named after John von Neumann, although it was first published by Ernst Zermelo in 1930.

https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Von_Neumann_Hierarchy.svg/450px-Von_Neumann_Hierarchy.svg.png
An initial segment of the von Neumann universe. Ordinal multiplication is reversed from our usual convention; see Ordinal arithmetic.

Finite and low cardinality stages of the hierarchy
The first five von Neumann stages V0 to V4 may be visualized as follows. (An empty box represents the empty set. A box containing only an empty box represents the set containing only the empty set, and so forth.)

https://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Von_Neumann_universe_4.png/1125px-Von_Neumann_universe_4.png
This sequence exhibits tetrational growth. The set V5 contains 2^16 = 65536 elements; the set V6 contains 2^65536 elements, which very substantially exceeds the number of atoms in the known universe; and for any natural n, the set Vn+1 contains 2 ↑↑ n elements using Knuth's up-arrow notation. So the finite stages of the cumulative hierarchy cannot be written down explicitly after stage 5. The set Vω has the same cardinality as ω. The set Vω+1 has the same cardinality as the set of real numbers.
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