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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 40 |
| 4 | 1120 |
| 5 | 91840 |
| 6 | 22408960 |
| 7 | 16358540800 |
| 8 | 35792487270400 |
| 9 | 234870301468364800 |
| 10 | 4623187014103292723200 |
| 11 | 272999193182799435304960000 |
| 12 | 48361261073946554365403054080000 |
| 13 | 25701205307660304745058529866383360000 |
| 14 | 40976048450930207702360695570691784048640000 |
[1,1,4,40,1120,91840,22408960,16358540800, 35792487270400,234870301468364800, 4623187014103292723200, 272999193182799435304960000, 48361261073946554365403054080000, 25701205307660304745058529866383360000, 40976048450930207702360695570691784048640000] |