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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 3 |
| 7 | 17 |
| 8 | 61 |
| 9 | 235 |
| 10 | 815 |
| 11 | 2563 |
| 12 | 7585 |
| 13 | 22277 |
| 14 | 62065 |
| 15 | 169489 |
| 16 | 452621 |
| 17 | 1191617 |
[0,0,0,0,1,3,17,61,235,815,2563,7585,22277,62065, 169489,452621,1191617] |