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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 31 |
| 4 | 154 |
| 5 | 819 |
| 6 | 4560 |
| 7 | 26244 |
| 8 | 154874 |
| 9 | 932074 |
| 10 | 5698745 |
| 11 | 35297535 |
| 12 | 221016593 |
| 13 | 1396717756 |
| 14 | 8896798020 |
| 15 | 57062237502 |
| 16 | 368201804973 |
| 17 | 2388587515239 |
| 18 | 15568995139404 |
| 19 | 101913055166811 |
| 20 | 669678357109300 |
| 21 | 4415837460391845 |
| 22 | 29210203356645090 |
[1,2,7,31,154,819,4560,26244,154874,932074, 5698745,35297535,221016593,1396717756,8896798020, 57062237502,368201804973,2388587515239, 15568995139404,101913055166811,669678357109300, 4415837460391845,29210203356645090] |