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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 710 |
| 7 | 4815 |
| 8 | 36650 |
| 9 | 308778 |
| 10 | 2850294 |
| 11 | 28602468 |
| 12 | 310041806 |
| 13 | 3610879857 |
| 14 | 44975227466 |
| 15 | 596677473990 |
| 16 | 8401332033264 |
| 17 | 125140942951896 |
| 18 | 1966223504686334 |
| 19 | 32501786913873447 |
| 20 | 563877339150924866 |
| 21 | 10245134152041643818 |
| 22 | 194553155073687332550 |
| 23 | 3854328529787275833204 |
[1,1,2,6,24,120,710,4815,36650,308778,2850294, 28602468,310041806,3610879857,44975227466, 596677473990,8401332033264,125140942951896, 1966223504686334,32501786913873447, 563877339150924866,10245134152041643818, 194553155073687332550,3854328529787275833204] |