How about
declare @prin decimal(10,2) = 100,
@rate decimal(10,8) = 18.0--13.33333333
;with numbers (n)--replace with your num table
as ( select n from (values(1),(2),(3),(4),(5),(6),(7))v(n)
)
select [Id] = n,
[no] = (@prin*@rate)/80.0,
[bal] = @prin - ((@prin*@rate)*(n-1))/80.0
from numbers
Nathan Skerl