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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 40 |
| 5 | 216 |
| 6 | 1296 |
| 7 | 9136 |
| 8 | 73088 |
| 9 | 658048 |
| 10 | 6580480 |
| 11 | 72386304 |
| 12 | 868635648 |
| 13 | 11292267520 |
| 14 | 158091745280 |
| 15 | 2371376195584 |
| 16 | 37942019129344 |
| 17 | 645014325264384 |
| 18 | 11610257854758912 |
| 19 | 220594899240681472 |
| 20 | 4411897984813629440 |
[0,1,2,10,40,216,1296,9136,73088,658048,6580480, 72386304,868635648,11292267520,158091745280, 2371376195584,37942019129344,645014325264384, 11610257854758912,220594899240681472, 4411897984813629440] |