To make a mobile station apparatus efficiently generate a base sequence. In a mobile station apparatus that generates a sequence for a demodulation reference signal on the basis of at least a sequence group number and transmits to a base station apparatus the demodulation reference signal together with a physical uplink shared channel used for transmission of a transport block, the mobile station apparatus receives information indicating a value of a parameter relating to the sequence from the base station apparatus, and determines the sequence group number without using the value of the parameter in a case where the mobile station apparatus performs transmission of the transport block on the physical uplink shared channel as part of a contention based random access procedure.