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| n | a(n) |
|---|---|
| 0 | -6 |
| 1 | -15 |
| 2 | -27 |
| 3 | 21 |
| 4 | 597 |
| 5 | 4437 |
| 6 | 25941 |
| 7 | 136533 |
| 8 | 677205 |
| 9 | 3233109 |
| 10 | 15029589 |
| 11 | 68506965 |
| 12 | 307582293 |
| 13 | 1364546901 |
| 14 | 5995058517 |
| 15 | 26127717717 |
| 16 | 113100805461 |
| 17 | 486762960213 |
| 18 | 2084490794325 |
| 19 | 8887718991189 |
[-6,-15,-27,21,597,4437,25941,136533,677205, 3233109,15029589,68506965,307582293,1364546901, 5995058517,26127717717,113100805461,486762960213, 2084490794325,8887718991189] |