A172520 - OEIS

A172520 as a triangular array

1

2 3

2 4 5

3 4 6 7

2 5 6 8 9

4 5 7 8 10 11

2 5 7 9 10 12 13

4 6 8 9 11 12 14 15

3 6 7 10 11 13 14 16 17

4 5 9 10 12 13 15 16 18 19

2 7 8 10 12 14 15 17 18 20 21

6 7 9 11 13 14 16 17 19 20 22 23

2 5 8 11 12

1 2 2 3 2 4 2 4 3 4 2 6 2

3 4 4 5 5 5 6 6 5 7 7 5

5 6 6 7 7 8 7 9 8 9 8

7 8 8 9 9 10 10 10 11 11

9 10 10 11 11 12 12 13 12

11 12 12 13 13 14 14

13 14 14 15 15 16

15 16 16 17 17

17 18 18 19

19 20 20

21 22

23