A simple problem

Formalize and prove that the product of two consecutive natural numbers is even.

Exercise 17

Formalize and prove that the product of three consecutive natural numbers is divisible by 2.

Exercise 18

Formalize and prove that the product of three consecutive natural numbers is divisible by 3.

Exercise 19

Formalize and prove that the product of three consecutive natural numbers is divisible by 6.

Exercise 20

Formalize and prove that the product of four consecutive natural numbers is divisible by 2.

Exercise 21

Formalize and prove that the product of four consecutive natural numbers is divisible by 3.

Exercise 22

Formalize and prove that the product of four consecutive natural numbers is divisible by 4.

Exercise 23

Formalize and prove that the product of four consecutive natural numbers is divisible by 6.

Exercise 24

Formalize and prove that the product of four consecutive natural numbers is divisible by 8.

Exercise 25

Formalize and prove that the product of four consecutive natural numbers is divisible by 12.

Exercise 26

Formalize and prove that the product of four consecutive natural numbers is divisible by 24.

Exercise 27

Formalize and prove that the product of five consecutive natural numbers is divisible by 120.

Interlude

Alfrothul: Wow.

Dana: Right.

Alfrothul: We have seen these numbers before.

Dana: You mean 2, 6, 24, and 120?

Alfrothul: Yes, the biggest of the divisors.

Bong-sun: Which begs the question.

Anton: The question?

Bong-sun: Well, if all these products are divisible, what is the result of the divisions?

Loki: Need a hand?

Anton (prudently): Er, yes?

Loki: Let me add one more exercise.

Exercise 28

Formalize and prove that the product of six consecutive natural numbers is divisible by 720.

Postlude

Mimer: Why, thank you, Loki.

Loki: You are most welcome.

Exercise 29

Perusing all the exercises above (without solving them, unless of course you absolutely need to) begs the following question: since the product of consecutive numbers is divisible by such other numbers, the result of these divisions by the largest possible such other number is a natural number. What is this natural number?

Credit

Thanks are due to Yves Bertot for the initial simple problem at this stage of the lecture notes.

Version

Created [22 Feb 2024]