I also noticed the Lars Pedersen and Birte Bentsdatter family. I found the marriage for them and see that they had children both before and after your Lars Pedersen and Birte Olsdatter. I had thought that possibly Birte Olsdatter could have been his second wife - but this is not the case.
It is strange that the family is not listed in the 1815 census. I also don't see Lars Pedersen in the 1801 census. I wonder if they arrived from a neighboring parish?Their 3 children were born at 3 different farms. They did move around a lot! I would suggest looking for info in neighboring parishes, also.