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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 57 |
| 4 | 614 |
| 5 | 7284 |
| 6 | 91566 |
| 7 | 1200705 |
| 8 | 16232820 |
| 9 | 224669049 |
| 10 | 3167546164 |
| 11 | 45332076360 |
| 12 | 656839389030 |
| 13 | 9616669678368 |
| 14 | 142047629163678 |
| 15 | 2114254565121153 |
| 16 | 31678697416852592 |
| 17 | 477435309876933207 |
| 18 | 7232846873430148224 |
| 19 | 110080098299375941607 |
| 20 | 1682316692754904517268 |
[0,1,6,57,614,7284,91566,1200705,16232820, 224669049,3167546164,45332076360,656839389030, 9616669678368,142047629163678,2114254565121153, 31678697416852592,477435309876933207, 7232846873430148224,110080098299375941607, 1682316692754904517268] |