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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 20 |
| 7 | 78 |
| 8 | 307 |
| 9 | 1486 |
| 10 | 6974 |
| 11 | 38584 |
| 12 | 212268 |
| 13 | 1321886 |
| 14 | 8186322 |
| 15 | 57015161 |
| 16 | 391153290 |
| 17 | 2976480926 |
| 18 | 22534577137 |
| 19 | 185638964675 |
| 20 | 1522358748758 |
| 21 | 13558705354828 |
| 22 | 119620910388056 |
| 23 | 1137343427864934 |
| 24 | 10770667246889494 |
| 25 | 108819371313460263 |
| 26 | 1095389086585963202 |
[1,1,0,1,2,6,20,78,307,1486,6974,38584,212268, 1321886,8186322,57015161,391153290,2976480926, 22534577137,185638964675,1522358748758, 13558705354828,119620910388056,1137343427864934, 10770667246889494,108819371313460263, 1095389086585963202] |