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B1 中级 英语 9:00 Educational

The Enormous TREE(3) - Numberphile

Numberphile · 2,005,907 次观看 · 添加于 3 周前

学习统计

B1

CEFR 等级

5/10

难度

字幕 (167 片段)

00:00

TONY PADILLA: A very very big number, a super super big number.

00:03

In fact, it's just an off-the-scale big number, and that's TREE(3).

00:08

It absolutely puts Graham's Number to shame.

00:11

I mean, really Graham's Number is effectively zero compared to TREE(3).

00:15

Let's explain where TREE(3) comes from.

00:17

Well, It comes from a game of trees.

00:19

There are three different types of seeds.

00:21

We're gonna have a green seed...

00:23

Mathematicians wouldn't call these seeds,

00:25

they'd call them nodes, but we'll call them seeds.

00:27

Okay, and a black seed, and a red seed.

00:30

And what we're gonna try and do is we're gonna try to build a forest.

00:34

Okay, one tree at a time.

00:36

The first tree can't have more than one seed.

00:39

The second tree can't have more than two seeds.

00:42

The third tree can't have more than three seeds and so on, okay?

00:45

And that's rule number one.

00:46

The other rule is that if you build a tree,

00:48

if you find that an earlier tree could've been contained within that tree,

00:53

the whole forest dies.

00:55

Okay? So let's just sort of illustrate what we mean,

00:58

so let's try and build a tree for example, so we might start off with,

01:02

you know, a green seed...

01:03

And then we branch up and we get a black seed...

01:07

And then maybe we have two branches...

01:09

And there, you know we can have another green seed maybe...

01:13

And we can sort of draw these trees, right?

01:15

We said that the first go, the first tree, shouldn't have more than one seed,

01:19

the second tree shouldn't have more than two seeds, and so on.

01:21

We also said if you build a tree,

01:23

then an earlier tree could've been contained within it, then the forest dies,

01:27

so what do we mean by contained?

01:29

Well the mathematical term that we're really talking about here is inf-embeddable.

01:33

Don't worry about what inf-embeddable is,

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