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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 54 |
| 5 | 442 |
| 6 | 4032 |
| 7 | 39706 |
| 8 | 413358 |
| 9 | 4487693 |
| 10 | 50348500 |
| 11 | 579994802 |
| 12 | 6827955072 |
| 13 | 81854670861 |
| 14 | 996529292432 |
| 15 | 12293898494952 |
| 16 | 153421680489694 |
| 17 | 1934041122204318 |
| 18 | 24599034335501730 |
| 19 | 315369011873625930 |
| 20 | 4072021557616191708 |
| 21 | 52915860528084306704 |
| 22 | 691646518495876375968 |
[1,1,2,8,54,442,4032,39706,413358,4487693, 50348500,579994802,6827955072,81854670861, 996529292432,12293898494952,153421680489694, 1934041122204318,24599034335501730, 315369011873625930,4072021557616191708, 52915860528084306704,691646518495876375968] |