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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 40 |
| 5 | 228 |
| 6 | 228 |
| 7 | 1440 |
| 8 | 4248 |
| 9 | 4248 |
| 10 | 60336 |
| 11 | 336528 |
| 12 | 336528 |
| 13 | 2172096 |
| 14 | 6363360 |
| 15 | 6363360 |
| 16 | 90922176 |
| 17 | 507352896 |
| 18 | 507352896 |
| 19 | 3273198336 |
| 20 | 9590514048 |
| 21 | 9590514048 |
| 22 | 137016168192 |
| 23 | 764553924864 |
| 24 | 764553924864 |
| 25 | 4932582054912 |
| 26 | 14452487659008 |
[0,1,2,2,40,228,228,1440,4248,4248,60336,336528, 336528,2172096,6363360,6363360,90922176,507352896, 507352896,3273198336,9590514048,9590514048, 137016168192,764553924864,764553924864, 4932582054912,14452487659008] |