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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 36 |
| 4 | 212 |
| 5 | 1324 |
| 6 | 8342 |
| 7 | 53302 |
| 8 | 343710 |
| 9 | 2232322 |
| 10 | 14582218 |
| 11 | 95702528 |
| 12 | 630544704 |
| 13 | 4168091856 |
| 14 | 27630031358 |
| 15 | 183604587444 |
| 16 | 1222672695812 |
| 17 | 8157398577024 |
| 18 | 54515075729370 |
| 19 | 364861668341252 |
| 20 | 2445239266293460 |
| 21 | 16407415704050100 |
[1,6,36,212,1324,8342,53302,343710,2232322, 14582218,95702528,630544704,4168091856, 27630031358,183604587444,1222672695812, 8157398577024,54515075729370,364861668341252, 2445239266293460,16407415704050100] |