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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 34 |
| 4 | 482 |
| 5 | 10056 |
| 6 | 286372 |
| 7 | 10591372 |
| 8 | 491169996 |
| 9 | 27826318000 |
| 10 | 1887581200256 |
| 11 | 150885500428224 |
| 12 | 14028718134958936 |
| 13 | 1500672248541122944 |
| 14 | 182987661921689610000 |
| 15 | 25231215606822797450176 |
[1,1,4,34,482,10056,286372,10591372,491169996, 27826318000,1887581200256,150885500428224, 14028718134958936,1500672248541122944, 182987661921689610000,25231215606822797450176] |