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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 18 |
| 4 | 252 |
| 5 | 4410 |
| 6 | 88734 |
| 7 | 1969668 |
| 8 | 47104056 |
| 9 | 1195658550 |
| 10 | 31891944750 |
| 11 | 887565934494 |
| 12 | 25639389304560 |
| 13 | 765765781572600 |
| 14 | 23574635888791804 |
| 15 | 746297727831434376 |
| 16 | 24247096863466015152 |
| 17 | 807243935471150901066 |
| 18 | 27503153109167182217082 |
| 19 | 957899411829034037383374 |
| 20 | 34073454839478198669105444 |
| 21 | 1236879534288183156526996062 |
| 22 | 45788365378826408823663436974 |
| 23 | 1727576456033196960394178300184 |
[1,2,18,252,4410,88734,1969668,47104056, 1195658550,31891944750,887565934494, 25639389304560,765765781572600,23574635888791804, 746297727831434376,24247096863466015152, 807243935471150901066,27503153109167182217082, 957899411829034037383374, 34073454839478198669105444, 1236879534288183156526996062, 45788365378826408823663436974, 1727576456033196960394178300184] |