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| n | a(n) |
|---|---|
| 5 | 1 |
| 6 | 4 |
| 7 | 13 |
| 8 | 28 |
| 9 | 49 |
| 10 | 96 |
| 11 | 501 |
| 12 | 3463 |
| 13 | 18127 |
| 14 | 74376 |
| 15 | 331418 |
| 16 | 2409920 |
| 17 | 26775212 |
| 18 | 305337017 |
| 19 | 3047283148 |
| 20 | 31207251008 |
| 21 | 409221933719 |
[1,4,13,28,49,96,501,3463,18127,74376,331418, 2409920,26775212,305337017,3047283148,31207251008, 409221933719] |