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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 24 |
| 5 | 78 |
| 6 | 268 |
| 7 | 956 |
| 8 | 3496 |
| 9 | 12998 |
| 10 | 48876 |
| 11 | 185268 |
| 12 | 706456 |
| 13 | 2706204 |
| 14 | 10404696 |
| 15 | 40124792 |
| 16 | 155133904 |
| 17 | 601113158 |
| 18 | 2333671756 |
| 19 | 9075266372 |
| 20 | 35345525944 |
| 21 | 137847053108 |
| 22 | 538258923016 |
| 23 | 2104101060872 |
| 24 | 8233434921904 |
| 25 | 32247612071708 |
| 26 | 126410623214968 |
| 27 | 495918566502536 |
[0,1,3,8,24,78,268,956,3496,12998,48876,185268, 706456,2706204,10404696,40124792,155133904, 601113158,2333671756,9075266372,35345525944, 137847053108,538258923016,2104101060872, 8233434921904,32247612071708,126410623214968, 495918566502536] |