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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 4 |
| 4 | 88 |
| 5 | 220 |
| 6 | 759 |
| 7 | 3303 |
| 8 | 11807 |
| 9 | 45995 |
| 10 | 161983 |
| 11 | 600598 |
| 12 | 2215104 |
| 13 | 8089252 |
| 14 | 30099028 |
| 15 | 109674718 |
| 16 | 406751671 |
| 17 | 1486387672 |
| 18 | 5496201882 |
| 19 | 20148470577 |
| 20 | 74325953662 |
| 21 | 272963769305 |
| 22 | 1005515372431 |
| 23 | 3696468960096 |
| 24 | 13607350428609 |
[0,4,4,88,220,759,3303,11807,45995,161983,600598, 2215104,8089252,30099028,109674718,406751671, 1486387672,5496201882,20148470577,74325953662, 272963769305,1005515372431,3696468960096, 13607350428609] |