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Try this beautiful problem from the American Invitational Mathematics Examination I, AIME I, 1997 based on Odd and Even integers.

Find the number of integers between 1 and 1000 that can be expressed as the difference of squares of two non-negative integers.

- is 107
- is 750
- is 840
- cannot be determined from the given information

Integers

Divisibility

Difference of squares

But try the problem first...

Answer: is 750.

Source

Suggested Reading

AIME I, 1997, Question 1

Elementary Number Theory by David Burton

First hint

Let x be a non-negetive integer \((x+1)^{2}-x^{2}=2x+1\)

Second Hint

Let y be a non-negetive integer \((y+1)^{2}-(y-1)^{2}=4y\)

Final Step

Numbers 2(mod 4) cannot be obtained as difference of squares then number of such numbers =500+250=750.

- https://www.cheenta.com/rational-number-and-integer-prmo-2019-question-9/
- https://www.youtube.com/watch?v=lBPFR9xequA

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