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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 48 |
| 5 | 177 |
| 6 | 732 |
| 7 | 2996 |
| 8 | 12795 |
| 9 | 55028 |
| 10 | 241501 |
| 11 | 1069045 |
| 12 | 4787070 |
| 13 | 21597011 |
| 14 | 98225888 |
| 15 | 449295301 |
| 16 | 2067428541 |
| 17 | 9558297415 |
| 18 | 44388651274 |
| 19 | 206939813507 |
| 20 | 968202646112 |
| 21 | 4544385974411 |
| 22 | 21391732227455 |
| 23 | 100965272325308 |
| 24 | 477704975876510 |
| 25 | 2265255087836236 |
| 26 | 10764023122312336 |
| 27 | 51246456066945366 |
[1,1,4,12,48,177,732,2996,12795,55028,241501, 1069045,4787070,21597011,98225888,449295301, 2067428541,9558297415,44388651274,206939813507, 968202646112,4544385974411,21391732227455, 100965272325308,477704975876510,2265255087836236, 10764023122312336,51246456066945366] |