Solution:
Let the 1984 consecutive positive integers be n,n+1,n+2,…,n+1983.
The sum of their squares is:
S=n2+(n+1)2+(n+2)2+⋯+(n+1983)2
This can be written as:
S=k=0∑1983(n+k)2=k=0∑1983(n2+2nk+k2)=1984n2+2nk=0∑1983k+k=0∑1983k2
We have:
k=0∑mk=2m(m+1)
k=0∑mk2=6m(m+1)(2m+1)
For m=1983:
k=0∑1983k=21983×1984
k=0∑1983k2=61983×1984×3967
So,
S=1984n2+2n⋅21983×1984+61983×1984×3967
=1984n2+1983×1984n+61983×1984×3967
Factor 1984:
1984=26×31.
Let us factor S as follows:
S=1984(n2+1983n)+61983×1984×3967
Let us factor 1983 and 3967:
1983=3×661
3967=2×1983+1
Let us write S as:
S=1984(n2+1983n+61983×3967)
But n2+1983n+61983×3967 is not necessarily an integer, so let's combine all terms over 6:
S=1984(n2+1983n+61983×3967)
=1984(66n2+6×1983n+1983×3967)
=61984(6n2+6×1983n+1983×3967)
Let us compute 6n2+6×1983n+1983×3967:
6n2+6×1983n=6n2+11898n
1983×3967=1983×(2×1983+1)=1983×2×1983+1983=2×19832+1983
19832=(2000−17)2=4,000,000−68,000+289=3,932,289
2×19832=7,864,578
2×19832+1983=7,864,578+1983=7,866,561
So the numerator is:
6n2+11898n+7,866,561
Therefore,
S=61984(6n2+11898n+7,866,561)
Now, 1984/6=992/3, so S=3992(6n2+11898n+7,866,561)
For S to be an integer, 6n2+11898n+7,866,561 must be divisible by 3.
But the main point is to show that S cannot be a perfect square for any integer n.
Let us consider the sum of k consecutive squares:
It is known that the sum of k consecutive squares cannot be a perfect square unless k=1 or k=24 (see, for example, Mordell's result).
But 1984 is not 1 or 24.
Alternatively, consider the sum modulo 4.
The square of any integer is congruent to 0 or 1 modulo 4.
Let us compute S modulo 4.
Since 1984 is divisible by 4, the sum S is divisible by 4.
But more generally, we can use the following result:
Suppose k is even and k≡2(mod4), then the sum of k consecutive squares cannot be a perfect square.
But 1984≡0(mod4), so this does not help.
Alternatively, consider modulo 3.
The squares modulo 3 are 0 and 1.
But the key is that for k>1, the sum of k consecutive squares cannot be a perfect square except for k=24 (see Dickson, History of the Theory of Numbers, Vol. II, p. 413).
Therefore, the sum of the squares of 1984 consecutive positive integers cannot be a perfect square.