As another approach, you can use reshape:
>>> a = torch.arange(12)
>>> a
tensor([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11])
>>> a.reshape(-1,3)[:,:2].reshape(-1)
tensor([ 0,  1,  3,  4,  6,  7,  9, 10])