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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 30 |
| 4 | 138 |
| 5 | 620 |
| 6 | 3060 |
| 7 | 14910 |
| 8 | 76650 |
| 9 | 390852 |
| 10 | 2063376 |
| 11 | 10832052 |
| 12 | 58264668 |
| 13 | 312123240 |
| 14 | 1702423008 |
| 15 | 9256786110 |
| 16 | 51036229530 |
| 17 | 280696824980 |
| 18 | 1560925457520 |
| 19 | 8663089672380 |
| 20 | 48512836025940 |
| 21 | 271229902496280 |
| 22 | 1527733861191720 |
| 23 | 8593482390429300 |
| 24 | 48642125421855420 |
| 25 | 275014629509319000 |
[1,2,8,30,138,620,3060,14910,76650,390852,2063376, 10832052,58264668,312123240,1702423008,9256786110, 51036229530,280696824980,1560925457520, 8663089672380,48512836025940,271229902496280, 1527733861191720,8593482390429300, 48642125421855420,275014629509319000] |