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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 52 |
| 3 | 348 |
| 4 | 2322 |
| 5 | 15500 |
| 6 | 103462 |
| 7 | 690610 |
| 8 | 4609826 |
| 9 | 30770620 |
| 10 | 205394096 |
| 11 | 1371006978 |
| 12 | 9151480836 |
| 13 | 61086196378 |
| 14 | 407750773322 |
| 15 | 2721739165358 |
| 16 | 18167627307952 |
| 17 | 121269034961780 |
| 18 | 809471627267722 |
| 19 | 5403228578160660 |
[1,8,52,348,2322,15500,103462,690610,4609826, 30770620,205394096,1371006978,9151480836, 61086196378,407750773322,2721739165358, 18167627307952,121269034961780,809471627267722, 5403228578160660] |