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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 39 |
| 4 | 332 |
| 5 | 3290 |
| 6 | 38994 |
| 7 | 517986 |
| 8 | 7762880 |
| 9 | 128029464 |
| 10 | 2311675560 |
| 11 | 45188359920 |
| 12 | 952047539112 |
| 13 | 21452758881528 |
| 14 | 515073388373712 |
| 15 | 13114579450948920 |
| 16 | 352881761400606720 |
| 17 | 10000259978380933440 |
| 18 | 297654582665846499264 |
| 19 | 9280441162956638320704 |
[1,1,6,39,332,3290,38994,517986,7762880,128029464, 2311675560,45188359920,952047539112, 21452758881528,515073388373712,13114579450948920, 352881761400606720,10000259978380933440, 297654582665846499264,9280441162956638320704] |