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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 150 |
| 6 | 918 |
| 7 | 6876 |
| 8 | 63018 |
| 9 | 589518 |
| 10 | 6272712 |
| 11 | 76110150 |
| 12 | 950826294 |
| 13 | 13044895668 |
| 14 | 197045295354 |
| 15 | 3070861314894 |
| 16 | 51493780503216 |
| 17 | 931608094164870 |
| 18 | 17371288788509142 |
| 19 | 344019296960858844 |
| 20 | 7251768315234745722 |
| 21 | 157314435990604845822 |
| 22 | 3591397708609454572248 |
| 23 | 86444118766100900895390 |
[1,2,6,24,150,918,6876,63018,589518,6272712, 76110150,950826294,13044895668,197045295354, 3070861314894,51493780503216,931608094164870, 17371288788509142,344019296960858844, 7251768315234745722,157314435990604845822, 3591397708609454572248,86444118766100900895390] |