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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 26 |
| 4 | 190 |
| 5 | 722 |
| 6 | 7770 |
| 7 | 50570 |
| 8 | 303614 |
| 9 | 4978898 |
| 10 | 28560946 |
| 11 | 249598010 |
| 12 | 3921446506 |
| 13 | 40463101850 |
| 14 | 312501134098 |
| 15 | 2922002830706 |
| 16 | 81019507028734 |
| 17 | 621574793581010 |
| 18 | 6971887587108882 |
| 19 | 67208089701951674 |
| 20 | 1804527636721939490 |
| 21 | 24767209606785282698 |
| 22 | 246837597799949869378 |
[1,2,6,26,190,722,7770,50570,303614,4978898, 28560946,249598010,3921446506,40463101850, 312501134098,2922002830706,81019507028734, 621574793581010,6971887587108882, 67208089701951674,1804527636721939490, 24767209606785282698,246837597799949869378] |