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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 0 |
| 5 | 1 |
| 6 | 6 |
| 7 | 3 |
| 8 | 16 |
| 9 | 18 |
| 10 | 122 |
| 11 | 97 |
| 12 | 2725 |
| 13 | 26457 |
| 14 | 10615 |
| 15 | 367132 |
| 16 | 158738 |
| 17 | 1356272 |
| 18 | 72423339 |
[1,0,1,0,1,6,3,16,18,122,97,2725,26457,10615, 367132,158738,1356272,72423339] |