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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 7 |
| 4 | 42 |
| 5 | 287 |
| 6 | 2186 |
| 7 | 18650 |
| 8 | 176408 |
| 9 | 1837189 |
| 10 | 20908724 |
| 11 | 258210463 |
| 12 | 3440203098 |
| 13 | 49202385314 |
| 14 | 752012692572 |
[0,0,1,7,42,287,2186,18650,176408,1837189, 20908724,258210463,3440203098,49202385314, 752012692572] |