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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 86 |
| 5 | 544 |
| 6 | 3904 |
| 7 | 31328 |
| 8 | 276798 |
| 9 | 2660564 |
| 10 | 27576614 |
| 11 | 306051500 |
| 12 | 3615559236 |
| 13 | 45241980928 |
| 14 | 597141146374 |
| 15 | 8283583741588 |
| 16 | 120393776421550 |
| 17 | 1828261719906800 |
| 18 | 28937578248560784 |
| 19 | 476355010859517352 |
| 20 | 8139464481630136242 |
| 21 | 144109168217154747856 |
| 22 | 2639508261422244889106 |
| 23 | 49940898467864797567140 |
| 24 | 974790619672853340925800 |
[1,1,4,16,86,544,3904,31328,276798,2660564, 27576614,306051500,3615559236,45241980928, 597141146374,8283583741588,120393776421550, 1828261719906800,28937578248560784, 476355010859517352,8139464481630136242, 144109168217154747856,2639508261422244889106, 49940898467864797567140,974790619672853340925800] |