t =

0

1

2

3

4

r = 0

s = 0

0

1

2

3

5

r = 0

s = 1

1

2

4

7

12

r = 0

s = 2

2

4

9

16

29

r = 0

s = 3

3

7

16

31

57

r = 0

s = 4

5

12

29

57

109