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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 32 |
| 3 | 172 |
| 4 | 804 |
| 5 | 3268 |
| 6 | 13500 |
| 7 | 54036 |
| 8 | 217060 |
| 9 | 870480 |
| 10 | 3486232 |
| 11 | 13953424 |
| 12 | 55838260 |
| 13 | 223388312 |
| 14 | 893634984 |
| 15 | 3574717300 |
[1,4,32,172,804,3268,13500,54036,217060,870480, 3486232,13953424,55838260,223388312,893634984, 3574717300] |