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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 21 |
| 4 | 172 |
| 5 | 1575 |
| 6 | 15414 |
| 7 | 157873 |
| 8 | 1671110 |
| 9 | 18136057 |
| 10 | 200714844 |
| 11 | 2256618493 |
| 12 | 25701805501 |
| 13 | 295922645873 |
| 14 | 3438679963250 |
| 15 | 40275747470685 |
| 16 | 474988710563570 |
| 17 | 5635642445166757 |
| 18 | 67223407456360545 |
| 19 | 805676877214778199 |
| 20 | 9697290469855248844 |
| 21 | 117167343239759493011 |
| 22 | 1420602968905561974227 |
[1,1,3,21,172,1575,15414,157873,1671110,18136057, 200714844,2256618493,25701805501,295922645873, 3438679963250,40275747470685,474988710563570, 5635642445166757,67223407456360545, 805676877214778199,9697290469855248844, 117167343239759493011,1420602968905561974227] |