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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 42 |
| 4 | 244 |
| 5 | 1504 |
| 6 | 9656 |
| 7 | 63856 |
| 8 | 431872 |
| 9 | 2972778 |
| 10 | 20756036 |
| 11 | 146627648 |
| 12 | 1046060836 |
| 13 | 7525452296 |
| 14 | 54530660832 |
| 15 | 397628393728 |
| 16 | 2915496099136 |
| 17 | 21481907631872 |
| 18 | 158975372309176 |
| 19 | 1181109256858096 |
| 20 | 8806197969093184 |
[1,2,8,42,244,1504,9656,63856,431872,2972778, 20756036,146627648,1046060836,7525452296, 54530660832,397628393728,2915496099136, 21481907631872,158975372309176,1181109256858096, 8806197969093184] |