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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 49 |
| 4 | 535 |
| 5 | 3906 |
| 6 | 24066 |
| 7 | 135255 |
| 8 | 717825 |
| 9 | 3662848 |
| 10 | 18158932 |
| 11 | 88043517 |
| 12 | 419348475 |
| 13 | 1968346446 |
| 14 | 9126412278 |
| 15 | 41875079155 |
| 16 | 190408381765 |
| 17 | 858989527020 |
| 18 | 3848282308584 |
| 19 | 17134038373689 |
| 20 | 75866264567775 |
| 21 | 334251455152090 |
[0,0,49,535,3906,24066,135255,717825,3662848, 18158932,88043517,419348475,1968346446,9126412278, 41875079155,190408381765,858989527020, 3848282308584,17134038373689,75866264567775, 334251455152090] |