oracle sequence

I need query to find list of sequence which has less than 20% of sequence numbers. 

SQL what % used the sequence is, e.g. take curr value of the sequence, take the max val and work out the remaining amount, then divide by the total to get the % usedSQL what % used the sequence is, e.g. take curr value of the sequence, take the max val and work out the remaining amount, then divide by the total to get the % used