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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 67 |
| 4 | 283 |
| 5 | 1198 |
| 6 | 5074 |
| 7 | 21493 |
| 8 | 91045 |
| 9 | 385672 |
| 10 | 1633732 |
| 11 | 6920599 |
| 12 | 29316127 |
| 13 | 124185106 |
| 14 | 526056550 |
| 15 | 2228411305 |
| 16 | 9439701769 |
| 17 | 39987218380 |
| 18 | 169388575288 |
| 19 | 717541519531 |
| 20 | 3039554653411 |
| 21 | 12875760133174 |
| 22 | 54542595186106 |
| 23 | 231046140877597 |
[1,4,16,67,283,1198,5074,21493,91045,385672, 1633732,6920599,29316127,124185106,526056550, 2228411305,9439701769,39987218380,169388575288, 717541519531,3039554653411,12875760133174, 54542595186106,231046140877597] |