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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 20 |
| 6 | 56 |
| 7 | 117 |
| 8 | 323 |
| 9 | 745 |
| 10 | 1896 |
| 11 | 4242 |
| 12 | 12883 |
| 13 | 29108 |
| 14 | 75725 |
| 15 | 183366 |
| 16 | 504215 |
| 17 | 1176776 |
[1,1,2,4,10,20,56,117,323,745,1896,4242,12883, 29108,75725,183366,504215,1176776] |