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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 19 |
| 4 | 145 |
| 5 | 1679 |
| 6 | 31146 |
| 7 | 919866 |
| 8 | 43716030 |
| 9 | 3345087696 |
| 10 | 413168662224 |
| 11 | 82432477483344 |
| 12 | 26585428576089600 |
| 13 | 13864587294260493504 |
| 14 | 11694921751248976025856 |
| 15 | 15957837208927564640940096 |
| 16 | 35227081534568618432596098240 |
[1,4,19,145,1679,31146,919866,43716030,3345087696, 413168662224,82432477483344,26585428576089600, 13864587294260493504,11694921751248976025856, 15957837208927564640940096, 35227081534568618432596098240] |