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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 11 |
| 3 | 52 |
| 4 | 227 |
| 5 | 944 |
| 6 | 3800 |
| 7 | 14944 |
| 8 | 57748 |
| 9 | 220128 |
| 10 | 829968 |
| 11 | 3101376 |
| 12 | 11502704 |
| 13 | 42393088 |
| 14 | 155392768 |
| 15 | 566918144 |
| 16 | 2059768384 |
| 17 | 7456496128 |
| 18 | 26905720576 |
| 19 | 96804463616 |
| 20 | 347386161920 |
| 21 | 1243665567744 |
| 22 | 4442849839104 |
| 23 | 15840448094208 |
[0,2,11,52,227,944,3800,14944,57748,220128,829968, 3101376,11502704,42393088,155392768,566918144, 2059768384,7456496128,26905720576,96804463616, 347386161920,1243665567744,4442849839104, 15840448094208] |