Nonlinear sequential fractional differential equations with nonlocal boundary conditions involving lower-order fractional derivatives

Abstract This paper studies a new class of boundary value problems of sequential fractional differential equations of order q ∈ ( 2 , 3 ] $q \in(2, 3]$ supplemented with nonlocal non-separated boundary conditions involving lower-order fractional derivatives. Existence and uniqueness results for the given problem are obtained by applying standard fixed-point theorems and are illustrated with the aid of examples. Some interesting observations are presented