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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | -1 |
| 3 | -6 |
| 4 | -15 |
| 5 | 20 |
| 6 | 303 |
| 7 | 742 |
| 8 | -2975 |
| 9 | -17784 |
| 10 | 101471 |
| 11 | 1089330 |
| 12 | -4112559 |
| 13 | -109689892 |
| 14 | -175956081 |
| 15 | 10257283678 |
| 16 | 62492991169 |
| 17 | -1187272882032 |
| 18 | -14383393311553 |
| 19 | 159864567511530 |
| 20 | 3401397735742641 |
| 21 | -22534114976850652 |
[1,0,-1,-6,-15,20,303,742,-2975,-17784,101471, 1089330,-4112559,-109689892,-175956081, 10257283678,62492991169,-1187272882032, -14383393311553,159864567511530,3401397735742641, -22534114976850652] |