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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 60 |
| 5 | 708 |
| 6 | 11428 |
| 7 | 232756 |
| 8 | 5704964 |
| 9 | 163192820 |
| 10 | 5331728964 |
| 11 | 195776203764 |
| 12 | 7978838333188 |
| 13 | 357313060904692 |
| 14 | 17438518614448580 |
| 15 | 921145685670017012 |
| 16 | 52355425184381107332 |
| 17 | 3185815887918686343924 |
| 18 | 206633438251087758833476 |
[1,1,2,8,60,708,11428,232756,5704964,163192820, 5331728964,195776203764,7978838333188, 357313060904692,17438518614448580, 921145685670017012,52355425184381107332, 3185815887918686343924,206633438251087758833476] |