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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 54 |
| 4 | 210 |
| 5 | 699 |
| 6 | 2484 |
| 7 | 7995 |
| 8 | 26610 |
| 9 | 84186 |
| 10 | 269940 |
| 11 | 839238 |
| 12 | 2634579 |
| 13 | 8098194 |
| 14 | 25032282 |
| 15 | 76388265 |
| 16 | 233791104 |
| 17 | 709501596 |
| 18 | 2157488730 |
| 19 | 6523204836 |
| 20 | 19747491810 |
| 21 | 59558682132 |
| 22 | 179762506329 |
| 23 | 541222906812 |
| 24 | 1630300772106 |
| 25 | 4902697929306 |
| 26 | 14748249476553 |
[1,3,15,54,210,699,2484,7995,26610,84186,269940, 839238,2634579,8098194,25032282,76388265, 233791104,709501596,2157488730,6523204836, 19747491810,59558682132,179762506329,541222906812, 1630300772106,4902697929306,14748249476553] |