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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 44 |
| 5 | 156 |
| 6 | 560 |
| 7 | 2049 |
| 8 | 7684 |
| 9 | 28772 |
| 10 | 108368 |
| 11 | 412396 |
| 12 | 1573776 |
| 13 | 6029488 |
| 14 | 23226176 |
| 15 | 89573577 |
| 16 | 346281380 |
| 17 | 1343190436 |
| 18 | 5216949776 |
| 19 | 20296197484 |
| 20 | 79131832976 |
| 21 | 308798743728 |
| 22 | 1206495306816 |
| 23 | 4720960267204 |
| 24 | 18487515792272 |
| 25 | 72463886990864 |
| 26 | 284340829780288 |
| 27 | 1116404838166192 |
| 28 | 4386449721693760 |
[1,1,4,13,44,156,560,2049,7684,28772,108368, 412396,1573776,6029488,23226176,89573577, 346281380,1343190436,5216949776,20296197484, 79131832976,308798743728,1206495306816, 4720960267204,18487515792272,72463886990864, 284340829780288,1116404838166192,4386449721693760] |