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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 54 |
| 5 | 546 |
| 6 | 7644 |
| 7 | 140388 |
| 8 | 3253608 |
| 9 | 92429592 |
| 10 | 3147053520 |
| 11 | 126146938608 |
| 12 | 5866848879168 |
| 13 | 312780729436704 |
| 14 | 18921429038592288 |
| 15 | 1287533798347045536 |
| 16 | 97808017722679006848 |
| 17 | 8240098982756882179968 |
| 18 | 765420628291191991328256 |
| 19 | 77987441816127455405628672 |
[1,1,2,8,54,546,7644,140388,3253608,92429592, 3147053520,126146938608,5866848879168, 312780729436704,18921429038592288, 1287533798347045536,97808017722679006848, 8240098982756882179968,765420628291191991328256, 77987441816127455405628672] |