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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 23 |
| 3 | 197 |
| 4 | 2056 |
| 5 | 23714 |
| 6 | 290512 |
| 7 | 3707852 |
| 8 | 48760367 |
| 9 | 656043857 |
| 10 | 8987427467 |
| 11 | 124936258127 |
| 12 | 1757900019101 |
| 13 | 24987199492705 |
| 14 | 358268702159069 |
| 15 | 5175497420902741 |
| 16 | 75254198337177848 |
| 17 | 1100534370899151722 |
| 18 | 16176618251666906476 |
| 19 | 238861285363295350240 |
[1,4,23,197,2056,23714,290512,3707852,48760367, 656043857,8987427467,124936258127,1757900019101, 24987199492705,358268702159069,5175497420902741, 75254198337177848,1100534370899151722, 16176618251666906476,238861285363295350240] |