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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 36 |
| 4 | 177 |
| 5 | 1300 |
| 6 | 8866 |
| 7 | 54849 |
| 8 | 372943 |
| 9 | 2466986 |
| 10 | 16335736 |
| 11 | 108823634 |
| 12 | 719573862 |
| 13 | 4776148981 |
| 14 | 31691581679 |
| 15 | 210171600724 |
| 16 | 1394511598079 |
| 17 | 9249464911748 |
| 18 | 61356588838016 |
| 19 | 407022840274446 |
| 20 | 2699962045755658 |
| 21 | 17910503042677994 |
| 22 | 118809774179725990 |
[1,1,3,36,177,1300,8866,54849,372943,2466986, 16335736,108823634,719573862,4776148981, 31691581679,210171600724,1394511598079, 9249464911748,61356588838016,407022840274446, 2699962045755658,17910503042677994, 118809774179725990] |