Some remarks on compositeness of T^+_cc

Recently LHCb experimental group find an exotic state T^+_cc from the process pp̅→ D^0D^0π^+ + X. A key question is if it is just a molecule or may have confined tetraquark ingredient. To investigate this, different methods are taken, including two channel (D^*+D^0 and D^*0D^+) K-matrix unitarization and single channel Flatté-like parametrization method analysed by pole counting rule and spectral density function sum rule. It demonstrates that T^+_cc is a molecular state, though the possibility that there may exist elementary ingredient can not be excluded, by rough analysis on its production rate.