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| n | a(n) |
|---|---|
| 6 | 1 |
| 7 | 4 |
| 8 | 13 |
| 9 | 45 |
| 10 | 194 |
| 11 | 809 |
| 12 | 3321 |
| 13 | 15727 |
| 14 | 81305 |
| 15 | 509040 |
| 16 | 3870198 |
| 17 | 33980590 |
| 18 | 341474106 |
[1,4,13,45,194,809,3321,15727,81305,509040, 3870198,33980590,341474106] |