How to tell which OTU include which Sequences?

Theory behind mothur
1

I have approximately 30000 OTUs and I would like to know which OTUs include which sequences?

2

All the sequences that make up each OTU are in the .list. It will take a little command line magic to pull the information (each OTU level is one line, the sequences in each OTU are comma separated, and each OTU is separated by a tab)