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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 109 |
| 6 | 618 |
| 7 | 4098 |
| 8 | 31173 |
| 9 | 267809 |
| 10 | 2565520 |
| 11 | 27120007 |
| 12 | 313616532 |
| 13 | 3938508241 |
| 14 | 53381045786 |
| 15 | 776672993274 |
| 16 | 12074274033482 |
| 17 | 199746500391688 |
| 18 | 3503656507826887 |
| 19 | 64951437702821877 |
| 20 | 1268898555348831913 |
| 21 | 26055882443142671038 |
| 22 | 561050228044941209930 |
| 23 | 12641053014560238560492 |
| 24 | 297439800300471548183778 |
[1,1,2,6,23,109,618,4098,31173,267809,2565520, 27120007,313616532,3938508241,53381045786, 776672993274,12074274033482,199746500391688, 3503656507826887,64951437702821877, 1268898555348831913,26055882443142671038, 561050228044941209930,12641053014560238560492, 297439800300471548183778] |