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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 21 |
| 6 | 54 |
| 7 | 161 |
| 8 | 470 |
| 9 | 1347 |
| 10 | 4007 |
| 11 | 12199 |
| 12 | 37141 |
| 13 | 113802 |
| 14 | 352905 |
| 15 | 1101969 |
| 16 | 3455220 |
| 17 | 10891968 |
| 18 | 34515825 |
| 19 | 109814395 |
| 20 | 350616323 |
| 21 | 1123368287 |
| 22 | 3610647348 |
| 23 | 11637410625 |
| 24 | 37605280548 |
| 25 | 121812321775 |
| 26 | 395455199269 |
| 27 | 1286446544052 |
| 28 | 4192913001804 |
| 29 | 13690359696969 |
[1,1,1,3,9,21,54,161,470,1347,4007,12199,37141, 113802,352905,1101969,3455220,10891968,34515825, 109814395,350616323,1123368287,3610647348, 11637410625,37605280548,121812321775,395455199269, 1286446544052,4192913001804,13690359696969] |