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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 14 |
| 3 | 50 |
| 4 | 191 |
| 5 | 780 |
| 6 | 3415 |
| 7 | 15924 |
| 8 | 78595 |
| 9 | 408337 |
| 10 | 2224365 |
| 11 | 12650992 |
| 12 | 74876950 |
| 13 | 459783611 |
| 14 | 2922921341 |
| 15 | 19192162340 |
| 16 | 129864598566 |
| 17 | 903840021981 |
| 18 | 6460209847133 |
| 19 | 47345351199234 |
| 20 | 355305371430875 |
| 21 | 2727065598788860 |
[1,4,14,50,191,780,3415,15924,78595,408337, 2224365,12650992,74876950,459783611,2922921341, 19192162340,129864598566,903840021981, 6460209847133,47345351199234,355305371430875, 2727065598788860] |