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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 9 |
| 6 | 20 |
| 7 | 47 |
| 8 | 112 |
| 9 | 276 |
| 10 | 684 |
| 11 | 1713 |
| 12 | 4295 |
| 13 | 10797 |
| 14 | 27103 |
| 15 | 67985 |
| 16 | 170202 |
| 17 | 425420 |
| 18 | 1061324 |
| 19 | 2643451 |
| 20 | 6573241 |
| 21 | 16321357 |
| 22 | 40469502 |
| 23 | 100219208 |
| 24 | 247888403 |
| 25 | 612467226 |
| 26 | 1511670488 |
| 27 | 3727408256 |
| 28 | 9182341969 |
| 29 | 22600453960 |
| 30 | 55579530018 |
[1,1,1,2,4,9,20,47,112,276,684,1713,4295,10797, 27103,67985,170202,425420,1061324,2643451,6573241, 16321357,40469502,100219208,247888403,612467226, 1511670488,3727408256,9182341969,22600453960, 55579530018] |