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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 40 |
| 3 | 602 |
| 4 | 8080 |
| 5 | 102002 |
| 6 | 1240120 |
| 7 | 14704202 |
| 8 | 171312160 |
| 9 | 1970527202 |
| 10 | 22450640200 |
| 11 | 253930611002 |
| 12 | 2855998840240 |
| 13 | 31980846315602 |
| 14 | 356873041128280 |
| 15 | 3971357037321002 |
| 16 | 44096709674720320 |
| 17 | 488769846799627202 |
| 18 | 5409822678195232360 |
| 19 | 59808238730741554202 |
[0,2,40,602,8080,102002,1240120,14704202, 171312160,1970527202,22450640200,253930611002, 2855998840240,31980846315602,356873041128280, 3971357037321002,44096709674720320, 488769846799627202,5409822678195232360, 59808238730741554202] |