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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 20 |
| 5 | 50 |
| 6 | 181 |
| 7 | 513 |
| 8 | 1981 |
| 9 | 6087 |
| 10 | 24450 |
| 11 | 79265 |
| 12 | 326192 |
| 13 | 1098561 |
| 14 | 4604660 |
| 15 | 15968636 |
| 16 | 67934917 |
| 17 | 241144724 |
| 18 | 1037831560 |
| 19 | 3753744245 |
| 20 | 16303956286 |
| 21 | 59889623003 |
| 22 | 262114436704 |
| 23 | 975484574708 |
| 24 | 4296973313554 |
| 25 | 16171297126704 |
| 26 | 71624751796375 |
| 27 | 272169868078628 |
| 28 | 1211149718585558 |
| 29 | 4641314003656235 |
[1,1,3,6,20,50,181,513,1981,6087,24450,79265, 326192,1098561,4604660,15968636,67934917, 241144724,1037831560,3753744245,16303956286, 59889623003,262114436704,975484574708, 4296973313554,16171297126704,71624751796375, 272169868078628,1211149718585558,4641314003656235] |