i live on the first floor of my building. everyday we come back after a walk me and my dog need to climb 7 stairs. forget about me, how many ways can my dog climb them if he climbs 1-2 stairs in one step.

eg. he may either climb the 7 stairs by climbing 2, then 2, then 2, then 1, or 1, then 2, then 2, then 2, or he may climb then as 2,2,1,1,1........in total, how may possible ways? thats all i mean.