Nonexistence of global solutions for a class of sequential fractional differential inequalities

We provide sufficient conditions for the non-existence of global solutions for a certain class of sequential fractional differential inequalities involving Riemann-Liouville left-sided fractional derivatives with different orders. To the best of our knowledge, the study of non-existence of solutions for fractional differential problems with sequential fractional derivatives has not been investigated until now. Our approach is based on the test function method.