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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 1 |
| 4 | 24 |
| 5 | 15 |
| 6 | 72 |
| 7 | 119 |
| 8 | 16 |
| 9 | 975 |
| 10 | 352 |
| 11 | 3615 |
| 12 | 896 |
| 13 | 14591 |
| 14 | 3200 |
| 15 | 50559 |
| 16 | 30976 |
| 17 | 157439 |
| 18 | 131584 |
| 19 | 260607 |
| 20 | 1068032 |
| 21 | 1991679 |
| 22 | 593920 |
| 23 | 16687103 |
| 24 | 6868992 |
| 25 | 51654655 |
| 26 | 9641984 |
| 27 | 226598911 |
| 28 | 16302080 |
| 29 | 1013858303 |
| 30 | 100859904 |
| 31 | 4092723199 |
| 32 | 429719552 |
| 33 | 15166799871 |
[1,0,6,1,24,15,72,119,16,975,352,3615,896,14591, 3200,50559,30976,157439,131584,260607,1068032, 1991679,593920,16687103,6868992,51654655,9641984, 226598911,16302080,1013858303,100859904, 4092723199,429719552,15166799871] |