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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 21 |
| 3 | 94 |
| 4 | 352 |
| 5 | 2133 |
| 6 | 11930 |
| 7 | 60772 |
| 8 | 326592 |
| 9 | 1772900 |
| 10 | 9465417 |
| 11 | 50680823 |
| 12 | 272327824 |
| 13 | 1460652327 |
| 14 | 7831666171 |
| 15 | 42016275835 |
| 16 | 225392908023 |
| 17 | 1208952350028 |
| 18 | 6484936659738 |
| 19 | 34786259866407 |
| 20 | 186595358346906 |
| 21 | 1000910649083880 |
[1,21,94,352,2133,11930,60772,326592,1772900, 9465417,50680823,272327824,1460652327,7831666171, 42016275835,225392908023,1208952350028, 6484936659738,34786259866407,186595358346906, 1000910649083880] |