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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 48 |
| 5 | 384 |
| 6 | 3872 |
| 7 | 47088 |
| 8 | 671360 |
| 9 | 10985088 |
| 10 | 202927872 |
| 11 | 4178030592 |
| 12 | 94874787840 |
| 13 | 2355758714880 |
| 14 | 63498696376320 |
| 15 | 1846607063998464 |
| 16 | 57630620308930560 |
| 17 | 1921296165774950400 |
| 18 | 68145277700464312320 |
| 19 | 2562234152415762972672 |
| 20 | 101801592691389968154624 |
[1,1,2,8,48,384,3872,47088,671360,10985088, 202927872,4178030592,94874787840,2355758714880, 63498696376320,1846607063998464,57630620308930560, 1921296165774950400,68145277700464312320, 2562234152415762972672,101801592691389968154624] |