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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 57 |
| 4 | 614 |
| 5 | 7716 |
| 6 | 104322 |
| 7 | 1529385 |
| 8 | 23689968 |
| 9 | 385885521 |
| 10 | 6531397090 |
| 11 | 114147452526 |
| 12 | 2045979734964 |
| 13 | 37435147640010 |
| 14 | 696431496524796 |
| 15 | 13134442980269397 |
| 16 | 250527556214516892 |
| 17 | 4824098879117797749 |
| 18 | 93639919777995946446 |
| 19 | 1830133457257882605430 |
[1,1,6,57,614,7716,104322,1529385,23689968, 385885521,6531397090,114147452526,2045979734964, 37435147640010,696431496524796,13134442980269397, 250527556214516892,4824098879117797749, 93639919777995946446,1830133457257882605430] |