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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 52 |
| 6 | 202 |
| 7 | 870 |
| 8 | 4084 |
| 9 | 20727 |
| 10 | 112825 |
| 11 | 654546 |
| 12 | 4026487 |
| 13 | 26145511 |
| 14 | 178550986 |
| 15 | 1278168860 |
| 16 | 9564026947 |
| 17 | 74615547996 |
| 18 | 605593775899 |
| 19 | 5103054929621 |
| 20 | 44564754448972 |
| 21 | 402677613100491 |
| 22 | 3759094788129312 |
| 23 | 36205919126040190 |
| 24 | 359340174509911325 |
| 25 | 3670825700549853053 |
[1,1,2,5,15,52,202,870,4084,20727,112825,654546, 4026487,26145511,178550986,1278168860,9564026947, 74615547996,605593775899,5103054929621, 44564754448972,402677613100491,3759094788129312, 36205919126040190,359340174509911325, 3670825700549853053] |