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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 8 |
| 3 | 72 |
| 4 | 604 |
| 5 | 5148 |
| 6 | 43544 |
| 7 | 368408 |
| 8 | 3112262 |
| 9 | 26273542 |
| 10 | 221605240 |
| 11 | 1867736120 |
| 12 | 15730022540 |
| 13 | 132385106956 |
| 14 | 1113413229000 |
| 15 | 9358220560136 |
| 16 | 78606905495809 |
| 17 | 659886123312449 |
| 18 | 5536404584185376 |
| 19 | 46424396382193376 |
| 20 | 389074608184431328 |
| 21 | 3259085506224931424 |
| 22 | 27286163457927575200 |
[1,1,8,72,604,5148,43544,368408,3112262,26273542, 221605240,1867736120,15730022540,132385106956, 1113413229000,9358220560136,78606905495809, 659886123312449,5536404584185376, 46424396382193376,389074608184431328, 3259085506224931424,27286163457927575200] |