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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 16 |
| 4 | 103 |
| 5 | 732 |
| 6 | 5534 |
| 7 | 43654 |
| 8 | 355219 |
| 9 | 2959796 |
| 10 | 25127182 |
| 11 | 216566228 |
| 12 | 1889981702 |
| 13 | 16667677502 |
| 14 | 148309034228 |
| 15 | 1329840823598 |
| 16 | 12004376548231 |
| 17 | 109001991366916 |
| 18 | 994928157018222 |
| 19 | 9123606773971816 |
| 20 | 84014017887712710 |
| 21 | 776551886860725700 |
| 22 | 7202290010661477580 |
[0,1,3,16,103,732,5534,43654,355219,2959796, 25127182,216566228,1889981702,16667677502, 148309034228,1329840823598,12004376548231, 109001991366916,994928157018222,9123606773971816, 84014017887712710,776551886860725700, 7202290010661477580] |