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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 14 |
| 5 | 53 |
| 6 | 265 |
| 7 | 1554 |
| 8 | 11024 |
| 9 | 90816 |
| 10 | 846032 |
| 11 | 8803826 |
| 12 | 101011765 |
| 13 | 1265197857 |
| 14 | 17167351014 |
| 15 | 250725968406 |
| 16 | 3920074915626 |
| 17 | 65310957981693 |
| 18 | 1154885557082749 |
| 19 | 21599009876309400 |
| 20 | 425919898969718528 |
| 21 | 8831294211199266816 |
| 22 | 192065262001816123136 |
[1,1,2,6,14,53,265,1554,11024,90816,846032, 8803826,101011765,1265197857,17167351014, 250725968406,3920074915626,65310957981693, 1154885557082749,21599009876309400, 425919898969718528,8831294211199266816, 192065262001816123136] |