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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 14 |
| 5 | 34 |
| 6 | 61 |
| 7 | 120 |
| 8 | 215 |
| 9 | 690 |
| 10 | 1144 |
| 11 | 2584 |
| 12 | 5626 |
| 13 | 13709 |
| 14 | 31275 |
| 15 | 63461 |
| 16 | 145767 |
| 17 | 340332 |
| 18 | 649190 |
| 19 | 1703684 |
| 20 | 4218462 |
| 21 | 10675070 |
| 22 | 22892978 |
[1,2,4,9,14,34,61,120,215,690,1144,2584,5626, 13709,31275,63461,145767,340332,649190,1703684, 4218462,10675070,22892978] |