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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 69 |
| 4 | 929 |
| 5 | 13692 |
| 6 | 213402 |
| 7 | 3456450 |
| 8 | 57585400 |
| 9 | 980408857 |
| 10 | 16982002433 |
| 11 | 298322996205 |
| 12 | 5302587890821 |
| 13 | 95196447689434 |
| 14 | 1723782813066284 |
| 15 | 31447947375375315 |
| 16 | 577509675356805547 |
| 17 | 10667460556561578780 |
| 18 | 198074286156460874227 |
| 19 | 3695152948440645726312 |
[1,1,6,69,929,13692,213402,3456450,57585400, 980408857,16982002433,298322996205,5302587890821, 95196447689434,1723782813066284,31447947375375315, 577509675356805547,10667460556561578780, 198074286156460874227,3695152948440645726312] |