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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 6 |
| 4 | 2 |
| 5 | 70 |
| 6 | 90 |
| 7 | 926 |
| 8 | 2002 |
| 9 | 13110 |
| 10 | 37130 |
| 11 | 194446 |
| 12 | 640002 |
| 13 | 2973350 |
| 14 | 10653370 |
| 15 | 46333566 |
| 16 | 174174002 |
| 17 | 730176790 |
| 18 | 2820264810 |
| 19 | 11582386286 |
| 20 | 45425564002 |
| 21 | 184414199430 |
| 22 | 729520967450 |
| 23 | 2942491360606 |
| 24 | 11696742970002 |
| 25 | 47006639297270 |
| 26 | 187367554937290 |
[1,0,6,2,70,90,926,2002,13110,37130,194446,640002, 2973350,10653370,46333566,174174002,730176790, 2820264810,11582386286,45425564002,184414199430, 729520967450,2942491360606,11696742970002, 47006639297270,187367554937290] |