RMAN :: How To List Archivelogs That Need Backup

I would like to rman command syntax only for the following scenarios.I have archivelogs the disk , sequence = 40, 41, 42 , 43and say, I backed up only sequence 41 file. next time I want to list (not backup) which archivelogfiles have not been backed up since the last backup (which was sequence 41 was backedup).I would like to be able to list 40, 42. 43 that needed to be backed up as a list in the RMAN. I understand that I can look at find from v$archived_log view and I can backup using (backup archivelog all not backed up 1 times to device type disk - i am ok with this).I need to be able to list the archivelogs that need backup from existing disk-directory of archivelog files from RMAN prompt.