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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 23 |
| 4 | 98 |
| 5 | 437 |
| 6 | 1995 |
| 7 | 9242 |
| 8 | 43258 |
| 9 | 204053 |
| 10 | 968441 |
| 11 | 4619012 |
| 12 | 22120631 |
| 13 | 106300508 |
| 14 | 512321438 |
| 15 | 2475395303 |
| 16 | 11986728458 |
| 17 | 58156146653 |
| 18 | 282640193313 |
| 19 | 1375737276788 |
| 20 | 6705522150973 |
| 21 | 32724071280518 |
| 22 | 159878425878848 |
[1,2,6,23,98,437,1995,9242,43258,204053,968441, 4619012,22120631,106300508,512321438,2475395303, 11986728458,58156146653,282640193313, 1375737276788,6705522150973,32724071280518, 159878425878848] |