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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 46 |
| 5 | 178 |
| 6 | 699 |
| 7 | 2826 |
| 8 | 11665 |
| 9 | 48877 |
| 10 | 207426 |
| 11 | 889753 |
| 12 | 3850726 |
| 13 | 16792923 |
| 14 | 73721417 |
| 15 | 325516893 |
| 16 | 1444683024 |
| 17 | 6440892041 |
| 18 | 28832816045 |
| 19 | 129544987197 |
| 20 | 583978531063 |
| 21 | 2640502004594 |
| 22 | 11972283977009 |
| 23 | 54421442961369 |
| 24 | 247958522736954 |
| 25 | 1132210929270549 |
| 26 | 5180203300927992 |
| 27 | 23745237667125709 |
[1,1,4,13,46,178,699,2826,11665,48877,207426, 889753,3850726,16792923,73721417,325516893, 1444683024,6440892041,28832816045,129544987197, 583978531063,2640502004594,11972283977009, 54421442961369,247958522736954,1132210929270549, 5180203300927992,23745237667125709] |