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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 81 |
| 5 | 535 |
| 6 | 5274 |
| 7 | 60684 |
| 8 | 869238 |
| 9 | 14595645 |
| 10 | 284939257 |
| 11 | 6347472749 |
| 12 | 159579271688 |
| 13 | 4482770916274 |
| 14 | 139578090353236 |
| 15 | 4783834092385411 |
| 16 | 179397242557917048 |
| 17 | 7322223973235272082 |
| 18 | 323760818899998259561 |
| 19 | 15443359560966718348986 |
| 20 | 791699492870169123493379 |
[1,1,3,12,81,535,5274,60684,869238,14595645, 284939257,6347472749,159579271688,4482770916274, 139578090353236,4783834092385411, 179397242557917048,7322223973235272082, 323760818899998259561,15443359560966718348986, 791699492870169123493379] |