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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 8 |
| 3 | 21 |
| 4 | 56 |
| 5 | 153 |
| 6 | 428 |
| 7 | 1221 |
| 8 | 3536 |
| 9 | 10353 |
| 10 | 30548 |
| 11 | 90621 |
| 12 | 269816 |
| 13 | 805353 |
| 14 | 2407868 |
| 15 | 7207221 |
| 16 | 21588896 |
| 17 | 64701153 |
| 18 | 193972388 |
| 19 | 581655021 |
| 20 | 1744440776 |
| 21 | 5232273753 |
| 22 | 15694724108 |
| 23 | 47079978021 |
| 24 | 141231545456 |
| 25 | 423677859153 |
| 26 | 1271000023028 |
| 27 | 3812932960221 |
| 28 | 11438664662936 |
[1,3,8,21,56,153,428,1221,3536,10353,30548,90621, 269816,805353,2407868,7207221,21588896,64701153, 193972388,581655021,1744440776,5232273753, 15694724108,47079978021,141231545456,423677859153, 1271000023028,3812932960221,11438664662936] |