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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 37 |
| 5 | 151 |
| 6 | 606 |
| 7 | 2426 |
| 8 | 9708 |
| 9 | 38835 |
| 10 | 155343 |
| 11 | 621377 |
| 12 | 2485512 |
| 13 | 9942052 |
| 14 | 39768214 |
| 15 | 159072861 |
| 16 | 636291449 |
| 17 | 2545165803 |
| 18 | 10180663218 |
| 19 | 40722652878 |
| 20 | 162890611520 |
| 21 | 651562446087 |
| 22 | 2606249784355 |
| 23 | 10424999137429 |
| 24 | 41699996549724 |
| 25 | 166799986198904 |
[0,0,2,9,37,151,606,2426,9708,38835,155343,621377, 2485512,9942052,39768214,159072861,636291449, 2545165803,10180663218,40722652878,162890611520, 651562446087,2606249784355,10424999137429, 41699996549724,166799986198904] |