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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 10 |
| 3 | 23 |
| 4 | 66 |
| 5 | 192 |
| 6 | 636 |
| 7 | 2092 |
| 8 | 7228 |
| 9 | 25175 |
| 10 | 89212 |
| 11 | 318808 |
| 12 | 1150444 |
| 13 | 4177908 |
| 14 | 15268494 |
| 15 | 56078527 |
| 16 | 206903020 |
| 17 | 766342160 |
| 18 | 2848351388 |
| 19 | 10619472284 |
| 20 | 39702648534 |
| 21 | 148806583111 |
| 22 | 558999381656 |
| 23 | 2104255629608 |
| 24 | 7936108068008 |
| 25 | 29982733437844 |
| 26 | 113456750715426 |
| 27 | 429964269551767 |
| 28 | 1631663320986086 |
[1,4,10,23,66,192,636,2092,7228,25175,89212, 318808,1150444,4177908,15268494,56078527, 206903020,766342160,2848351388,10619472284, 39702648534,148806583111,558999381656, 2104255629608,7936108068008,29982733437844, 113456750715426,429964269551767,1631663320986086] |