Observations about the division of squares by prime numbers
Euler begins with a review of the fundamental properties of quadratic residues, as outlined in E242, e.g. conditions for -1 to be a quadratic residue (Theorems 4 and 5).
Original Source Citation
Opuscula analytica, Volume 1, pp. 64-84.
Opera Omnia Citation
Series 1, Volume 3, pp.497-512.