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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 17 |
| 5 | 95 |
| 6 | 594 |
| 7 | 4280 |
| 8 | 35018 |
| 9 | 320636 |
| 10 | 3249951 |
| 11 | 36140133 |
| 12 | 437572800 |
| 13 | 5731086422 |
| 14 | 80745062993 |
| 15 | 1217782176949 |
| 16 | 19576722067015 |
| 17 | 334183547442139 |
| 18 | 6037316140379389 |
| 19 | 115082343658784617 |
| 20 | 2308352556410956084 |
| 21 | 48602560660569621128 |
| 22 | 1071794851776260190000 |
[1,1,1,3,17,95,594,4280,35018,320636,3249951, 36140133,437572800,5731086422,80745062993, 1217782176949,19576722067015,334183547442139, 6037316140379389,115082343658784617, 2308352556410956084,48602560660569621128, 1071794851776260190000] |