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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 30 |
| 5 | 272 |
| 6 | 4717 |
| 7 | 5402 |
| 8 | 18487 |
| 9 | 20115 |
| 10 | 28372 |
| 11 | 33998 |
| 12 | 111040 |
| 13 | 115170 |
| 14 | 456975 |
| 15 | 821586 |
| 16 | 1874660 |
| 17 | 4029676 |
| 18 | 4060029 |
| 19 | 59497900 |
| 20 | 232668002 |
| 21 | 313128068 |
| 22 | 529436220 |
[1,4,12,30,272,4717,5402,18487,20115,28372,33998, 111040,115170,456975,821586,1874660,4029676, 4060029,59497900,232668002,313128068,529436220] |