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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 8 |
| 3 | 102 |
| 4 | 1952 |
| 5 | 49920 |
| 6 | 1603392 |
| 7 | 62100304 |
| 8 | 2818386944 |
| 9 | 146748098304 |
| 10 | 8624885719040 |
| 11 | 564885716972544 |
| 12 | 40800979548180480 |
| 13 | 3222148806557544448 |
| 14 | 276214603877715378176 |
| 15 | 25544721442331112192000 |
| 16 | 2535168741071076287971328 |
| 17 | 268757182971129822376624128 |
| 18 | 30311086789573678207758237696 |
[1,1,8,102,1952,49920,1603392,62100304,2818386944, 146748098304,8624885719040,564885716972544, 40800979548180480,3222148806557544448, 276214603877715378176,25544721442331112192000, 2535168741071076287971328, 268757182971129822376624128, 30311086789573678207758237696] |