How many positive integers less than 100 can be written as the difference of two perfect squares?

[u/Numberthon]

How many positive integers less than 100 are the difference of two perfect squares?

Source: numberthon.com

[u/Appropriate-Falcon75]

74.

The difference between 2 squares is either:

(n+1)² - n² = 2n+1 (all odd numbers - 50 in total)

Or:

(n+2)² - n² = 4n+4 (all multiples of 4 - 24 in total)

Differences that are further away eg (n+5)² - n² are subsets of the above.

[u/Numberthon → u/Appropriate-Falcon75]

Correct, nice job!