Nonlinear Analysis and Applied Mathematics (NA AM)-Research Group;
Department of Mathematics;
Faculty of Science;
King Abdulaziz University;
P.O. Box 80203;
Jeddah 21589;
Saudi Arabia;
Department of Mathematics;
University of Ioannina;
451 10 Ioannina;
Greece Nonlinear Analysis and Applied Mathematics (NA AM)-Research Group;
Department of Mathematics;
Faculty of Science;
King Abdulaziz University;
P. O. Box 80203;
Jeddah 21589;
Saudi Arabia;
Coupled; system; sequential; fractional; derivative; multi-point; integral; boundary; conditions; existence;