A pair ( a , b ) of positive integers is pythagorean if 2 + = □ i.e. square). called double-pythapotent there another k l such that pair, and it quadratic pythapotent which not multiple pair. To each we assign an elliptic curve Γ with torsion group Z / × 4 has rank over Q only Similarly, to 8 Moreover, in the later case obtain every isomorphic form where As side-result get then are infinitely m...

Motivated by some properties satisfied Gorenstein projective and injective modules over an Iwanaga-Gorenstein ring, we present the concept of left right n-cotorsion pairs in abelian category C. Two classes A B objects C form a pair (A,B) if orthogonality relation ExtCi(A,B)=0 is for indexes 1≤i≤n, every object has resolution whose syzygies have B-resolution dimension at most n−1. This its dual ...