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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 52 |
| 5 | 177 |
| 6 | 807 |
| 7 | 3041 |
| 8 | 14268 |
| 9 | 56590 |
| 10 | 270028 |
| 11 | 1106952 |
| 12 | 5339922 |
| 13 | 22402560 |
| 14 | 108879743 |
| 15 | 464602037 |
| 16 | 2270119906 |
| 17 | 9813344344 |
| 18 | 48139440999 |
| 19 | 210239624137 |
| 20 | 1034441748942 |
| 21 | 4555286272410 |
| 22 | 22466061317387 |
| 23 | 99610665420191 |
| 24 | 492185173300521 |
| 25 | 2194832280561287 |
| 26 | 10861273254989284 |
| 27 | 48671943604817077 |
[1,1,4,12,52,177,807,3041,14268,56590,270028, 1106952,5339922,22402560,108879743,464602037, 2270119906,9813344344,48139440999,210239624137, 1034441748942,4555286272410,22466061317387, 99610665420191,492185173300521,2194832280561287, 10861273254989284,48671943604817077] |