<ヒント> >>620より再録 https://encyclopediaofmath.org/wiki/Ordinal_number Encyclopedia of Mathematics Ordinal number transfinite number, ordinal
A transfinite sequence of type α, or an α-sequence, is a function φ defined on {β?β<α}. If the values of this sequence are ordinal numbers, and if γ<β<α implies that φ(γ)<φ(β), then it is called an ascending sequence. (引用終り) 以上