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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 48 |
| 6 | 140 |
| 7 | 424 |
| 8 | 1280 |
| 9 | 3920 |
| 10 | 12032 |
| 11 | 37184 |
| 12 | 115248 |
| 13 | 358624 |
| 14 | 1118784 |
| 15 | 3499584 |
| 16 | 10969344 |
| 17 | 34450944 |
| 18 | 108377984 |
| 19 | 341465344 |
| 20 | 1077300224 |
| 21 | 3403006464 |
| 22 | 10761447424 |
| 23 | 34065967104 |
| 24 | 107937899264 |
| 25 | 342293526016 |
| 26 | 1086339120128 |
| 27 | 3450236511232 |
| 28 | 10965437349888 |
[1,1,2,6,16,48,140,424,1280,3920,12032,37184, 115248,358624,1118784,3499584,10969344,34450944, 108377984,341465344,1077300224,3403006464, 10761447424,34065967104,107937899264,342293526016, 1086339120128,3450236511232,10965437349888] |