Similar to Δ-システム補題

1 + 1 + 1 + 1 + ⋯

1/2 + 1/4 + 1/8 + 1/16 + ⋯

1/2 − 1/4 + 1/8 − 1/16 + ⋯

1/4 + 1/16 + 1/64 + 1/256 + ⋯

Hundredth

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Set theory

Template:Set theory

Extension (semantics)

Intension

Set (mathematics)

Aronszajn tree

Hereditarily finite set

Universe (mathematics)

Euler diagram

Ω-logic