Finding Individual Dates Having Dates Plus 2 Days

I want to find the dates which have a date plus with in 2 days after this date. I mean group by 3 days each even the date i missing between two days. Actualy I want to find the start date where the employ was missing on job.

Basic concept is employes have allowed to use 10 personal leaves of a year. Each leave can be use for maximum 3 days.

If employ did not come on the job for one day or two days or three days, it shoul be count as ONE personal leave. And If employ is missing at job for four or five days, it should be count as 2 personal leaves.

seq date
------------------------------
101.01.10

205.01.10
306.01.10

410.01.10
512.01.10

613.01.10
714.01.10
815.01.10

916.01.10
1018.01.10

1119.01.10
1220.01.10
1321.01.10

1423.01.10

1526.01.10
1627.01.10

1729.01.10
1831.01.10

The result should be (Don't use Pl/Sql)

seq date
------------------------------
101.01.10
205.01.10
310.01.10
413.01.10
516.01.10
619.01.10
723.01.10
826.01.10
929.01.10

After finding these days I want to select the starting date of 5th personal leave. (which is 16.01.10).

I am not a expert of using SQL, but I think it could be possible with using partitioning a table on the givin reslult and further partition the reslut on rownum() as rn and the using case statement where rn = 5.