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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 6 |
| 6 | 29 |
| 7 | 604 |
| 8 | 69724 |
| 9 | 49836144 |
| 10 | 250872492816 |
| 11 | 10113420362487552 |
| 12 | 3669877057922582621184 |
| 13 | 13317216838086531218401935360 |
| 14 | 531580547910000731718546175028428800 |
| 15 | 254627927130379381409123944181515703549952000 |
[0,0,1,2,3,6,29,604,69724,49836144,250872492816, 10113420362487552,3669877057922582621184, 13317216838086531218401935360, 531580547910000731718546175028428800, 254627927130379381409123944181515703549952000] |