Prove the following:
If there is one perfect square in an arithmetic progression, then there are infinitely many.

(In reply to Counterexample by Steve Herman)

Even in the positive reals: 4+pi, 4+2pi,.... I rather doubt there is another square in the sequence.

A different matter if a and d are both in the positive integers.

Update: it's also true if a and d are in the positive rationals.

Edited on March 28, 2018, 9:30 am

Posted by broll on 2018-03-28 08:52:00