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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 42 |
| 3 | 492 |
| 4 | 4060 |
| 5 | 26070 |
| 6 | 137886 |
| 7 | 623576 |
| 8 | 2476296 |
| 9 | 8809110 |
| 10 | 28512110 |
| 11 | 85014204 |
| 12 | 235895244 |
| 13 | 614266354 |
| 14 | 1511679210 |
| 15 | 3536846160 |
| 16 | 7907476016 |
| 17 | 16967926746 |
| 18 | 35078339106 |
| 19 | 70098276620 |
| 20 | 135798494460 |
| 21 | 255689552382 |
| 22 | 468969729382 |
| 23 | 839584669992 |
| 24 | 1469778991800 |
| 25 | 2520031983950 |
[2,42,492,4060,26070,137886,623576,2476296, 8809110,28512110,85014204,235895244,614266354, 1511679210,3536846160,7907476016,16967926746, 35078339106,70098276620,135798494460,255689552382, 468969729382,839584669992,1469778991800, 2520031983950] |