Looking for an algorithm

Question

I'm trying to make an algorithm that writes the following:
1   0
2   1
3   2
4   3
5   3
6   4
7   5
8   6
9   6
10   7
11   8
12   9
13   9
14  10
15  11
16  12
17  12
18  13
19  14
20  15The numer to the left is just a counter. The number to the right is a variable that counts upwards
based on the counter.
Anyone got any nifty ideas? And, before anyone hints at it: I have tried, but I'm not very good at this kind of thing :-)

Answer 1

Sure. I forgot to post what I really wanted to to, because I first posted the question in another forum.
Well. It's supposed to be an algorithm that makes these columns, simple because I want it rather than just typing in a lot of variables. The left column is a counter, which represents the level. The right one is the BAB, which is supposed to be as the column I posted first, based on the level.
                    for(int i=0 ; i<=level-1 ; i++) {
                         bab = i ;
                         if ((i+1)%4 == 1)
                         bab = i-1 ;
                         System.out.println((i+1) +" " +bab) ;               
                    }This gives this output;
1     -1
2     1
3     2
4     3
5     3
6     5
7     6
8     7
9     7
10   9
11   10
12   11
13   11
14   13
15   14
16   15
17   15
18   17
19   18
20   19The pattern for the second column is supposed to be this:
when the counter reaches a number which is devidable with 4 (4,8,12 and 16), the next counter number
is supposed to be the same, ie. not increment. Then on the next counter thereafter it should continue counting.
I've got some of it, as you can see, but the problem is that when it continues it increments 2 instead of 1. (counter 6 should be give 4, and not 5).