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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 38 |
| 5 | 190 |
| 6 | 1146 |
| 7 | 8022 |
| 8 | 64200 |
| 9 | 577800 |
| 10 | 5778120 |
| 11 | 63559320 |
| 12 | 762712560 |
| 13 | 9915263280 |
| 14 | 138813690960 |
| 15 | 2082205364400 |
| 16 | 33315285870720 |
| 17 | 566359859802240 |
| 18 | 10194477476803200 |
| 19 | 193695072059260800 |
| 20 | 3873901441188844800 |
| 21 | 81351930264965740800 |
| 22 | 1789742465829286214400 |
[1,1,3,9,38,190,1146,8022,64200,577800,5778120, 63559320,762712560,9915263280,138813690960, 2082205364400,33315285870720,566359859802240, 10194477476803200,193695072059260800, 3873901441188844800,81351930264965740800, 1789742465829286214400] |