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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 14 |
| 3 | 49 |
| 4 | 173 |
| 5 | 616 |
| 6 | 2210 |
| 7 | 7982 |
| 8 | 29002 |
| 9 | 105944 |
| 10 | 388892 |
| 11 | 1433797 |
| 12 | 5307365 |
| 13 | 19717440 |
| 14 | 73496730 |
| 15 | 274797330 |
| 16 | 1030334910 |
| 17 | 3873215640 |
| 18 | 14595139140 |
| 19 | 55120449930 |
| 20 | 208601520114 |
| 21 | 790972319472 |
| 22 | 3004615788884 |
| 23 | 11432740177564 |
[1,4,14,49,173,616,2210,7982,29002,105944,388892, 1433797,5307365,19717440,73496730,274797330, 1030334910,3873215640,14595139140,55120449930, 208601520114,790972319472,3004615788884, 11432740177564] |