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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 10 |
| 4 | 18 |
| 5 | 35 |
| 6 | 49 |
| 7 | 108 |
| 8 | 181 |
| 9 | 346 |
| 10 | 651 |
| 11 | 1236 |
| 12 | 2348 |
| 13 | 4240 |
| 14 | 8454 |
| 15 | 16537 |
| 16 | 30963 |
| 17 | 60986 |
| 18 | 118814 |
| 19 | 225337 |
| 20 | 438305 |
| 21 | 854049 |
[2,6,10,18,35,49,108,181,346,651,1236,2348,4240, 8454,16537,30963,60986,118814,225337,438305, 854049] |