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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 31 |
| 4 | 153 |
| 5 | 806 |
| 6 | 4440 |
| 7 | 25266 |
| 8 | 147364 |
| 9 | 876282 |
| 10 | 5292527 |
| 11 | 32378125 |
| 12 | 200218715 |
| 13 | 1249456536 |
| 14 | 7858638756 |
| 15 | 49766595855 |
| 16 | 317051378103 |
| 17 | 2030589300596 |
| 18 | 13066646029059 |
| 19 | 84439101344619 |
| 20 | 547746622599561 |
| 21 | 3565472378360110 |
| 22 | 23282050305073680 |
| 23 | 152466688160732190 |
[1,2,7,31,153,806,4440,25266,147364,876282, 5292527,32378125,200218715,1249456536,7858638756, 49766595855,317051378103,2030589300596, 13066646029059,84439101344619,547746622599561, 3565472378360110,23282050305073680, 152466688160732190] |