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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6480 |
| 3 | 157680 |
| 4 | 1596510 |
| 5 | 9488016 |
| 6 | 40681440 |
| 7 | 140492880 |
| 8 | 406046520 |
| 9 | 1047312720 |
| 10 | 2426695200 |
| 11 | 5208293520 |
| 12 | 10421250750 |
| 13 | 19873356480 |
| 14 | 35716191840 |
| 15 | 62355291696 |
| 16 | 104234541390 |
| 17 | 169488573120 |
| 18 | 267064691760 |
| 19 | 413777075760 |
| 20 | 619573504896 |
| 21 | 920235334320 |
| 22 | 1331744781600 |
[1,0,6480,157680,1596510,9488016,40681440, 140492880,406046520,1047312720,2426695200, 5208293520,10421250750,19873356480,35716191840, 62355291696,104234541390,169488573120, 267064691760,413777075760,619573504896, 920235334320,1331744781600] |