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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 60 |
| 4 | 384 |
| 5 | 2752 |
| 6 | 19436 |
| 7 | 132888 |
| 8 | 938448 |
| 9 | 6977712 |
| 10 | 52748180 |
| 11 | 402295360 |
| 12 | 3045774336 |
| 13 | 22798000896 |
| 14 | 169191995264 |
| 15 | 1244649595008 |
| 16 | 9253079696256 |
| 17 | 69936818500032 |
| 18 | 532964898123840 |
| 19 | 4089541311972480 |
| 20 | 31558707924799104 |
[1,2,10,60,384,2752,19436,132888,938448,6977712, 52748180,402295360,3045774336,22798000896, 169191995264,1244649595008,9253079696256, 69936818500032,532964898123840,4089541311972480, 31558707924799104] |