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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 421 |
| 3 | 4064 |
| 4 | 3316 |
| 5 | 17828 |
| 6 | 104969 |
| 7 | 532511 |
| 8 | 1932168 |
| 9 | 7608792 |
| 10 | 40495097 |
| 11 | 193959222 |
| 12 | 806044112 |
| 13 | 3571553560 |
| 14 | 16732139668 |
| 15 | 77717205902 |
| 16 | 345532208087 |
| 17 | 1548242747664 |
| 18 | 7108827463856 |
| 19 | 32520170426142 |
| 20 | 146833013273650 |
| 21 | 664181788383321 |
[0,421,4064,3316,17828,104969,532511,1932168, 7608792,40495097,193959222,806044112,3571553560, 16732139668,77717205902,345532208087, 1548242747664,7108827463856,32520170426142, 146833013273650,664181788383321] |