A026820 as a triangular array
| | | | | | | | | | | | 1 |
| | | | | | | | | | | | 1 | | 2 |
| | | | | | | | | | | 1 | | 2 | | 3 |
| | | | | | | | | | 1 | | 3 | | 4 | | 5 |
| | | | | | | | | 1 | | 3 | | 5 | | 6 | | 7 |
| | | | | | | | 1 | | 4 | | 7 | | 9 | | 10 | | 11 |
| | | | | | | 1 | | 4 | | 8 | | 11 | | 13 | | 14 | | 15 |
| | | | | | 1 | | 5 | | 10 | | 15 | | 18 | | 20 | | 21 | | 22 |
| | | | | 1 | | 5 | | 12 | | 18 | | 23 | | 26 | | 28 | | 29 | | 30 |
| | | | 1 | | 6 | | 14 | | 23 | | 30 | | 35 | | 38 | | 40 | | 41 | | 42 |
| | | 1 | | 6 | | 16 | | 27 | | 37 | | 44 | | 49 | | 52 | | 54 | | 55 | | 56 |
| | 1 | | 7 | | 19 | | 34 | | 47 | | 58 | | 65 | | 70 | | 73 | | 75 | | 76 | | 77 |
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A026820 as a square array
1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1
| 2 | 2 | 3 | 3 | 4 | 4 | 5 | 5 | 6 | 6 | 7
| 3 | 4 | 5 | 7 | 8 | 10 | 12 | 14 | 16 | 19
| 5 | 6 | 9 | 11 | 15 | 18 | 23 | 27 | 34
| 7 | 10 | 13 | 18 | 23 | 30 | 37 | 47
| 11 | 14 | 20 | 26 | 35 | 44 | 58
| 15 | 21 | 28 | 38 | 49 | 65
| 22 | 29 | 40 | 52 | 70
| 30 | 41 | 54 | 73
| 42 | 55 | 75
| 56 | 76
| 77
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A026820 as an upper right triangle
1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1
| | 2 | 2 | 3 | 3 | 4 | 4 | 5 | 5 | 6 | 6 | 7
| | | 3 | 4 | 5 | 7 | 8 | 10 | 12 | 14 | 16 | 19
| | | | 5 | 6 | 9 | 11 | 15 | 18 | 23 | 27 | 34
| | | | | 7 | 10 | 13 | 18 | 23 | 30 | 37 | 47
| | | | | | 11 | 14 | 20 | 26 | 35 | 44 | 58
| | | | | | | 15 | 21 | 28 | 38 | 49 | 65
| | | | | | | | 22 | 29 | 40 | 52 | 70
| | | | | | | | | 30 | 41 | 54 | 73
| | | | | | | | | | 42 | 55 | 75
| | | | | | | | | | | 56 | 76
| | | | | | | | | | | | 77
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