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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 72 |
| 5 | 10 |
| 6 | 3600 |
| 7 | 1575 |
| 8 | 2800 |
| 9 | 1764 |
| 10 | 14112 |
| 11 | 13475 |
| 12 | 34927200 |
| 13 | 2316600 |
| 14 | 192192 |
| 15 | 4459455 |
| 16 | 4994589600 |
| 17 | 262061800 |
| 18 | 735869534400 |
| 19 | 17476901442 |
| 20 | 422721728 |
| 21 | 353723760 |
| 22 | 31127690880 |
| 23 | 10150725585 |
| 24 | 59637542956992 |
| 25 | 2205530434800 |
| 26 | 155748568976000 |
| 27 | 50956005028500 |
[1,1,4,9,72,10,3600,1575,2800,1764,14112,13475, 34927200,2316600,192192,4459455,4994589600, 262061800,735869534400,17476901442,422721728, 353723760,31127690880,10150725585,59637542956992, 2205530434800,155748568976000,50956005028500] |