The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 1 |
| 6 | 1 |
| 7 | 2 |
| 8 | 2 |
| 9 | 3 |
| 10 | 5 |
| 11 | 6 |
| 12 | 9 |
| 13 | 9 |
| 14 | 11 |
| 15 | 13 |
| 16 | 15 |
| 17 | 17 |
| 18 | 18 |
| 19 | 20 |
| 20 | 23 |
[0,0,0,1,1,1,2,2,3,5,6,9,9,11,13,15,17,18,20,23] |