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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 106 |
| 6 | 565 |
| 7 | 3399 |
| 8 | 22678 |
| 9 | 165646 |
| 10 | 1311334 |
| 11 | 11161529 |
| 12 | 101478038 |
| 13 | 980157177 |
| 14 | 10011461983 |
| 15 | 107712637346 |
| 16 | 1216525155129 |
| 17 | 14380174353934 |
| 18 | 177440071258827 |
| 19 | 2280166654498540 |
| 20 | 30450785320307436 |
| 21 | 421820687108853017 |
| 22 | 6050801956624661417 |
| 23 | 89738550379292147192 |
[1,1,2,6,23,106,565,3399,22678,165646,1311334, 11161529,101478038,980157177,10011461983, 107712637346,1216525155129,14380174353934, 177440071258827,2280166654498540, 30450785320307436,421820687108853017, 6050801956624661417,89738550379292147192] |