Let where gives the largest integer less than or equal to Then how many distinct numbers are there in the sequence
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Now consider putting two consecutive positive integers as a difference of two squares so that the difference is 104, if not around 104. This is also represented as ( n + 1 ) 2 − n 2 = 1 0 4 .
and we get 2 n + 1 = 1 0 4 n = 5 1 . 5
But n is not an integer, so let n = 5 2 .
Now subbing in n = 5 2 gives us ( n + 1 ) 2 − n 2 = 1 0 5 > 1 0 4
And 1 0 4 1 0 5 > 1 and this means that the floor function of any term from n = 5 2 will have a difference of at least one and thus the terms after n = 5 2 are distinct.
And thus, every term before n = 5 2 may or may not be distinct. The common difference of each term, 2 n + 1 < 1 0 4 . But 1 0 4 5 2 2 = 2 6 . So this means there are 2 6 − 0 + 1 = 2 7 distinct terms in the range 1 ≤ n ≤ 5 2 .
Now for the range 5 3 ≤ n ≤ 1 0 3 , since the common difference of 2 n + 1 > 1 0 4 , each of the term in the range 5 3 ≤ n ≤ 1 0 3 is distinct, so there are 1 0 3 − 5 3 + 1 = 5 1 distinct terms in the range 5 3 ≤ n ≤ 1 0 3 .
Thus, there are 2 7 + 5 1 = 7 8 distinct terms in all.