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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 20 |
| 3 | 438 |
| 4 | 16680 |
| 5 | 973034 |
| 6 | 80252732 |
| 7 | 8859646110 |
| 8 | 1258403748432 |
| 9 | 223202277906386 |
| 10 | 48295209177888356 |
| 11 | 12510350648500199814 |
| 12 | 3820068667490198035320 |
| 13 | 1357281805972469318509754 |
[0,2,20,438,16680,973034,80252732,8859646110, 1258403748432,223202277906386,48295209177888356, 12510350648500199814,3820068667490198035320, 1357281805972469318509754] |