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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 16 |
| 3 | 132 |
| 4 | 1034 |
| 5 | 8134 |
| 6 | 64880 |
| 7 | 525132 |
| 8 | 4307512 |
| 9 | 35750473 |
| 10 | 299759200 |
| 11 | 2535849836 |
| 12 | 21619615164 |
| 13 | 185582339740 |
| 14 | 1602675301920 |
| 15 | 13915031036412 |
| 16 | 121396437548136 |
| 17 | 1063653520870612 |
| 18 | 9355905795325888 |
| 19 | 82585983533819920 |
| 20 | 731350409249262330 |
| 21 | 6495673923406863630 |
[0,1,16,132,1034,8134,64880,525132,4307512, 35750473,299759200,2535849836,21619615164, 185582339740,1602675301920,13915031036412, 121396437548136,1063653520870612,9355905795325888, 82585983533819920,731350409249262330, 6495673923406863630] |