The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 10 |
| 6 | 15 |
| 7 | 21 |
| 8 | 28 |
| 9 | 36 |
| 10 | 45 |
| 11 | 55 |
| 12 | 66 |
| 13 | 78 |
| 14 | 91 |
| 15 | 105 |
| 16 | 300 |
| 17 | 406 |
| 18 | 703 |
| 19 | 903 |
| 20 | 3003 |
| 21 | 4005 |
| 22 | 8001 |
[0,1,3,6,10,15,21,28,36,45,55,66,78,91,105,300, 406,703,903,3003,4005,8001] |