- #1
Frillth
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Homework Statement
I need to find all arithmetic sequences of integers with the property that the sum of the first n terms is a perfect square for all integers n.
Homework Equations
a_n = nth term of the sequence = a_1 + (n-1)d
d = common difference
Sum of the first n terms of the sequence = n[2a_1+(n-1)d]/2
The Attempt at a Solution
I know that the sequence 1, 3, 5, 7, 9... sums to a perfect square every time, as will 1x^2, 3x^2, 5x^2..., with x being any integer.
This is the only way I can find to make the sequence sum to a perfect square every time. If this isn't the only way, what are the others? If this is, how can I prove it is the only way?