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| n | a(n) |
|---|---|
| 0 | -1 |
| 1 | -1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 8 |
| 6 | 18 |
| 7 | 33 |
| 8 | 68 |
| 9 | 124 |
| 10 | 250 |
| 11 | 460 |
| 12 | 922 |
| 13 | 1714 |
| 14 | 3430 |
| 15 | 6433 |
| 16 | 12868 |
| 17 | 24308 |
| 18 | 48618 |
| 19 | 92376 |
| 20 | 184754 |
| 21 | 352714 |
| 22 | 705430 |
| 23 | 1352076 |
| 24 | 2704154 |
| 25 | 5200298 |
| 26 | 10400598 |
| 27 | 20058298 |
| 28 | 40116598 |
| 29 | 77558758 |
| 30 | 155117518 |
| 31 | 300540193 |
| 32 | 601080388 |
| 33 | 1166803108 |
| 34 | 2333606218 |
| 35 | 4537567648 |
| 36 | 9075135298 |
| 37 | 17672631898 |
| 38 | 35345263798 |
| 39 | 68923264408 |
| 40 | 137846528818 |
[-1,-1,0,1,4,8,18,33,68,124,250,460,922,1714,3430, 6433,12868,24308,48618,92376,184754,352714,705430, 1352076,2704154,5200298,10400598,20058298, 40116598,77558758,155117518,300540193,601080388, 1166803108,2333606218,4537567648,9075135298, 17672631898,35345263798,68923264408,137846528818] |