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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 48 |
| 5 | 150 |
| 6 | 180 |
| 7 | 980 |
| 8 | 2240 |
| 9 | 5670 |
| 10 | 6300 |
| 11 | 30492 |
| 12 | 11088 |
| 13 | 156156 |
| 14 | 168168 |
| 15 | 257400 |
| 16 | 1647360 |
| 17 | 3719430 |
| 18 | 3938220 |
| 19 | 17551820 |
| 20 | 18475600 |
| 21 | 81477396 |
| 22 | 85357272 |
| 23 | 373173528 |
| 24 | 389398464 |
| 25 | 1690097500 |
| 26 | 1757701400 |
| 27 | 7582037400 |
| 28 | 3931426800 |
| 29 | 33738060600 |
[0,1,4,18,48,150,180,980,2240,5670,6300,30492, 11088,156156,168168,257400,1647360,3719430, 3938220,17551820,18475600,81477396,85357272, 373173528,389398464,1690097500,1757701400, 7582037400,3931426800,33738060600] |