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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 9 |
| 3 | 35 |
| 4 | 143 |
| 5 | 648 |
| 6 | 3071 |
| 7 | 15126 |
| 8 | 76495 |
| 9 | 395086 |
| 10 | 2074699 |
| 11 | 11044027 |
| 12 | 59457897 |
| 13 | 323180520 |
| 14 | 1771081641 |
| 15 | 9774955015 |
| 16 | 54286011887 |
| 17 | 303138215322 |
| 18 | 1701016909235 |
| 19 | 9586701364893 |
| 20 | 54241695455421 |
| 21 | 307991483403216 |
| 22 | 1754468491846461 |
[1,4,9,35,143,648,3071,15126,76495,395086,2074699, 11044027,59457897,323180520,1771081641,9774955015, 54286011887,303138215322,1701016909235, 9586701364893,54241695455421,307991483403216, 1754468491846461] |