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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 19 |
| 6 | 140 |
| 7 | 956 |
| 8 | 6506 |
| 9 | 45659 |
| 10 | 336996 |
| 11 | 2643979 |
| 12 | 22160244 |
| 13 | 198618081 |
| 14 | 1901082872 |
| 15 | 19381817300 |
| 16 | 209829985306 |
| 17 | 2404750030651 |
| 18 | 29088407474132 |
| 19 | 370369420974335 |
| 20 | 4951491489003676 |
| 21 | 69348849926870881 |
| 22 | 1015423795024288712 |
[0,0,0,0,2,19,140,956,6506,45659,336996,2643979, 22160244,198618081,1901082872,19381817300, 209829985306,2404750030651,29088407474132, 370369420974335,4951491489003676, 69348849926870881,1015423795024288712] |