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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -1 |
| 2 | 3 |
| 3 | 1 |
| 4 | 41 |
| 5 | 171 |
| 6 | 799 |
| 7 | 2633 |
| 8 | 7881 |
| 9 | 24391 |
| 10 | 99611 |
| 11 | 461649 |
| 12 | 2252953 |
| 13 | 10773491 |
| 14 | 46602711 |
| 15 | 176413201 |
| 16 | 596116769 |
| 17 | 1899975183 |
| 18 | 6302881171 |
| 19 | 24136694081 |
| 20 | 105765310281 |
| 21 | 476455493179 |
| 22 | 2033813426063 |
| 23 | 8019234229401 |
| 24 | 29410337173561 |
| 25 | 102444237073751 |
| 26 | 347418130583499 |
[1,-1,3,1,41,171,799,2633,7881,24391,99611,461649, 2252953,10773491,46602711,176413201,596116769, 1899975183,6302881171,24136694081,105765310281, 476455493179,2033813426063,8019234229401, 29410337173561,102444237073751,347418130583499] |