>>641 補足
179 名前：１３２人目の素数さん[] 投稿日：2021/06/17(木) 11:25:31.78 ID:1ixenOss [3/10]
>>178
上昇列の定義を確認したかったが見つからなかったので、自分で考えてみたが、
インデックス集合をIとして∀i,j∈I i≦j⇒ai≦ajが成り立つことかと思った
この場合、I={0, …, ω}から任意に2元i,jを取ってくると、i≦j⇒i=ai≦aj=jは自明に成り立つので、
a:{0, …, ω}→{0, …, ω}でa(x)=xとなる列は上昇列になるかなと
(引用終り)

ここ、下記の英文wikipediaに定義ある
上記の定義で合っている

https://en.wikipedia.org/wiki/Sequence
Sequence
2.3 Increasing and decreasing
A sequence is said to be monotonically increasing if each term is greater than or equal to the one before it.
For example, the sequence (a_n)_{n=1}^{∞} is monotonically increasing if and only if an+1 ≧ an for all n ∈ N.
If each consecutive term is strictly greater than (>) the previous term then the sequence is called strictly monotonically increasing.
A sequence is monotonically decreasing, if each consecutive term is less than or equal to the previous one, and strictly monotonically decreasing, if each is strictly less than the previous.
If a sequence is either increasing or decreasing it is called a monotone sequence.
This is a special case of the more general notion of a monotonic function.

The terms nondecreasing and nonincreasing are often used in place of increasing and decreasing in order to avoid any possible confusion with strictly increasing and strictly decreasing, respectively.