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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 4 |
| 3 | 18 |
| 4 | 64 |
| 5 | 210 |
| 6 | 664 |
| 7 | 2058 |
| 8 | 6304 |
| 9 | 19170 |
| 10 | 58024 |
| 11 | 175098 |
| 12 | 527344 |
| 13 | 1586130 |
| 14 | 4766584 |
| 15 | 14316138 |
| 16 | 42981184 |
| 17 | 129009090 |
| 18 | 387158344 |
| 19 | 1161737178 |
| 20 | 3485735824 |
| 21 | 10458256050 |
| 22 | 31376865304 |
| 23 | 94134790218 |
| 24 | 282412759264 |
| 25 | 847255055010 |
| 26 | 2541798719464 |
| 27 | 7625463267258 |
| 28 | 22876524019504 |
| 29 | 68629840493970 |
[0,0,4,18,64,210,664,2058,6304,19170,58024,175098, 527344,1586130,4766584,14316138,42981184, 129009090,387158344,1161737178,3485735824, 10458256050,31376865304,94134790218,282412759264, 847255055010,2541798719464,7625463267258, 22876524019504,68629840493970] |